import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.InputMismatchException;
import java.util.List;
import java.util.Map;

public class Main {

	private static final String NO = "NO";
	private static final String YES = "YES";
	InputStream is;
	PrintWriter out;
	String INPUT = "";

	private static final long MOD = 1000000007;
	private static final long inf = 100000000000L;

	void solve() {
		int T = 1;
		for (int i = 0; i < T; i++)
			solve(i);
	}

	void solve(int T) {
		long n = nl();
		long sum = 0;
		long p = 1;
		int cnt = 1;
		while (true) {
			p *= 26;
			if (sum + p < n) {
				sum += p;
				cnt++;
			}
			else
				break;
//			tr(sum);
		}
		n-=sum+1;
		char ans[] = new char[cnt];
		for (int i=0; i<cnt; i++) {
			ans[cnt-1-i]=(char) ('a'+n%26);
			n/=26;
		}
		
		out.println(new String(ans));
	}

	// a^b
	long power(long a, long b) {
		long x = 1, y = a;
		while (b > 0) {
			if (b % 2 != 0) {
				x = (x * y) % MOD;
			}
			y = (y * y) % MOD;
			b /= 2;
		}
		return x % MOD;
	}

	private long gcd(long a, long b) {
		while (a != 0) {
			long tmp = b % a;
			b = a;
			a = tmp;
		}
		return b;
	}

	void run() throws Exception {
		is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
		out = new PrintWriter(System.out);

		long s = System.currentTimeMillis();
		solve();
		out.flush();
		if (!INPUT.isEmpty())
			tr(System.currentTimeMillis() - s + "ms");
	}

	public static void main(String[] args) throws Exception {
		new Main().run();
	}

	private byte[] inbuf = new byte[1024];
	public int lenbuf = 0, ptrbuf = 0;
	private boolean vis[];

	private int readByte() {
		if (lenbuf == -1)
			throw new InputMismatchException();
		if (ptrbuf >= lenbuf) {
			ptrbuf = 0;
			try {
				lenbuf = is.read(inbuf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (lenbuf <= 0)
				return -1;
		}
		return inbuf[ptrbuf++];
	}

	private boolean isSpaceChar(int c) {
		return !(c >= 33 && c <= 126);
	}

	private int skip() {
		int b;
		while ((b = readByte()) != -1 && isSpaceChar(b))
			;
		return b;
	}

	private double nd() {
		return Double.parseDouble(ns());
	}

	private char nc() {
		return (char) skip();
	}

	private String ns() {
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while (!(isSpaceChar(b))) { // when nextLine, (isSpaceChar(b) && b != '
									// ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}

	private char[] ns(int n) {
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while (p < n) {
			if (!(isSpaceChar(b)))
				buf[p++] = (char) b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	}

	private char[][] nm(int n, int m) {
		char[][] map = new char[n][];
		for (int i = 0; i < n; i++)
			map[i] = ns(m);
		return map;
	}

	private int[] na(int n) {
		int[] a = new int[n];
		for (int i = 0; i < n; i++)
			a[i] = ni();
		return a;
	}

	private List<Integer> na2(int n) {
		List<Integer> a = new ArrayList<Integer>();
		for (int i = 0; i < n; i++)
			a.add(ni());
		return a;
	}

	private int[][] na(int n, int m) {
		int[][] a = new int[n][];
		for (int i = 0; i < n; i++)
			a[i] = na(m);
		return a;
	}

	private int ni() {
		int num = 0, b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-') {
			minus = true;
			b = readByte();
		}

		while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		}
	}

	private long[] nl(int n) {
		long[] a = new long[n];
		for (int i = 0; i < n; i++)
			a[i] = nl();
		return a;
	}

	private long[][] nl(int n, int m) {
		long[][] a = new long[n][];
		for (int i = 0; i < n; i++)
			a[i] = nl(m);
		return a;
	}

	private long nl() {
		long num = 0;
		int b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-') {
			minus = true;
			b = readByte();
		}

		while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		}
	}

	private static void tr(Object... o) {
		System.out.println(Arrays.deepToString(o));
	}

	public class Pair<K, V> {

		/**
		 * Key of this <code>Pair</code>.
		 */
		private K key;

		/**
		 * Gets the key for this pair.
		 * 
		 * @return key for this pair
		 */
		public K getKey() {
			return key;
		}

		/**
		 * Value of this this <code>Pair</code>.
		 */
		private V value;

		/**
		 * Gets the value for this pair.
		 * 
		 * @return value for this pair
		 */
		public V getValue() {
			return value;
		}

		/**
		 * Creates a new pair
		 * 
		 * @param key   The key for this pair
		 * @param value The value to use for this pair
		 */
		public Pair(K key, V value) {
			this.key = key;
			this.value = value;
		}

		/**
		 * <p>
		 * <code>String</code> representation of this <code>Pair</code>.
		 * </p>
		 *
		 * <p>
		 * The default name/value delimiter '=' is always used.
		 * </p>
		 *
		 * @return <code>String</code> representation of this <code>Pair</code>
		 */
		@Override
		public String toString() {
			return key + "=" + value;
		}

		/**
		 * <p>
		 * Generate a hash code for this <code>Pair</code>.
		 * </p>
		 *
		 * <p>
		 * The hash code is calculated using both the name and the value of the
		 * <code>Pair</code>.
		 * </p>
		 *
		 * @return hash code for this <code>Pair</code>
		 */
		@Override
		public int hashCode() {
			// name's hashCode is multiplied by an arbitrary prime number (13)
			// in order to make sure there is a difference in the hashCode between
			// these two parameters:
			// name: a value: aa
			// name: aa value: a
			return key.hashCode() * 13 + (value == null ? 0 : value.hashCode());
		}

		/**
		 * <p>
		 * Test this <code>Pair</code> for equality with another <code>Object</code>.
		 * </p>
		 *
		 * <p>
		 * If the <code>Object</code> to be tested is not a <code>Pair</code> or is
		 * <code>null</code>, then this method returns <code>false</code>.
		 * </p>
		 *
		 * <p>
		 * Two <code>Pair</code>s are considered equal if and only if both the names and
		 * values are equal.
		 * </p>
		 *
		 * @param o the <code>Object</code> to test for equality with this
		 *          <code>Pair</code>
		 * @return <code>true</code> if the given <code>Object</code> is equal to this
		 *         <code>Pair</code> else <code>false</code>
		 */
		@Override
		public boolean equals(Object o) {
			if (this == o)
				return true;
			if (o instanceof Pair) {
				Pair pair = (Pair) o;
				if (key != null ? !key.equals(pair.key) : pair.key != null)
					return false;
				if (value != null ? !value.equals(pair.value) : pair.value != null)
					return false;
				return true;
			}
			return false;
		}
	}

} import java.io.ByteArrayInputStream; ByteArrayInputStream java.io import java.io.IOException; IOException java.io import java.io.InputStream; InputStream java.io import java.io.PrintWriter; PrintWriter java.io import java.util.ArrayList; ArrayList java.util import java.util.Arrays; Arrays java.util import java.util.HashMap; HashMap java.util import java.util.InputMismatchException; InputMismatchException java.util import java.util.List; List java.util import java.util.Map; Map java.util public class Main {

	private static final String NO = "NO";
	private static final String YES = "YES";
	InputStream is;
	PrintWriter out;
	String INPUT = "";

	private static final long MOD = 1000000007;
	private static final long inf = 100000000000L;

	void solve() {
		int T = 1;
		for (int i = 0; i < T; i++)
			solve(i);
	}

	void solve(int T) {
		long n = nl();
		long sum = 0;
		long p = 1;
		int cnt = 1;
		while (true) {
			p *= 26;
			if (sum + p < n) {
				sum += p;
				cnt++;
			}
			else
				break;
//			tr(sum);
		}
		n-=sum+1;
		char ans[] = new char[cnt];
		for (int i=0; i<cnt; i++) {
			ans[cnt-1-i]=(char) ('a'+n%26);
			n/=26;
		}
		
		out.println(new String(ans));
	}

	// a^b
	long power(long a, long b) {
		long x = 1, y = a;
		while (b > 0) {
			if (b % 2 != 0) {
				x = (x * y) % MOD;
			}
			y = (y * y) % MOD;
			b /= 2;
		}
		return x % MOD;
	}

	private long gcd(long a, long b) {
		while (a != 0) {
			long tmp = b % a;
			b = a;
			a = tmp;
		}
		return b;
	}

	void run() throws Exception {
		is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
		out = new PrintWriter(System.out);

		long s = System.currentTimeMillis();
		solve();
		out.flush();
		if (!INPUT.isEmpty())
			tr(System.currentTimeMillis() - s + "ms");
	}

	public static void main(String[] args) throws Exception {
		new Main().run();
	}

	private byte[] inbuf = new byte[1024];
	public int lenbuf = 0, ptrbuf = 0;
	private boolean vis[];

	private int readByte() {
		if (lenbuf == -1)
			throw new InputMismatchException();
		if (ptrbuf >= lenbuf) {
			ptrbuf = 0;
			try {
				lenbuf = is.read(inbuf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (lenbuf <= 0)
				return -1;
		}
		return inbuf[ptrbuf++];
	}

	private boolean isSpaceChar(int c) {
		return !(c >= 33 && c <= 126);
	}

	private int skip() {
		int b;
		while ((b = readByte()) != -1 && isSpaceChar(b))
			;
		return b;
	}

	private double nd() {
		return Double.parseDouble(ns());
	}

	private char nc() {
		return (char) skip();
	}

	private String ns() {
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while (!(isSpaceChar(b))) { // when nextLine, (isSpaceChar(b) && b != '
									// ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}

	private char[] ns(int n) {
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while (p < n) {
			if (!(isSpaceChar(b)))
				buf[p++] = (char) b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	}

	private char[][] nm(int n, int m) {
		char[][] map = new char[n][];
		for (int i = 0; i < n; i++)
			map[i] = ns(m);
		return map;
	}

	private int[] na(int n) {
		int[] a = new int[n];
		for (int i = 0; i < n; i++)
			a[i] = ni();
		return a;
	}

	private List<Integer> na2(int n) {
		List<Integer> a = new ArrayList<Integer>();
		for (int i = 0; i < n; i++)
			a.add(ni());
		return a;
	}

	private int[][] na(int n, int m) {
		int[][] a = new int[n][];
		for (int i = 0; i < n; i++)
			a[i] = na(m);
		return a;
	}

	private int ni() {
		int num = 0, b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-') {
			minus = true;
			b = readByte();
		}

		while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		}
	}

	private long[] nl(int n) {
		long[] a = new long[n];
		for (int i = 0; i < n; i++)
			a[i] = nl();
		return a;
	}

	private long[][] nl(int n, int m) {
		long[][] a = new long[n][];
		for (int i = 0; i < n; i++)
			a[i] = nl(m);
		return a;
	}

	private long nl() {
		long num = 0;
		int b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-') {
			minus = true;
			b = readByte();
		}

		while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		}
	}

	private static void tr(Object... o) {
		System.out.println(Arrays.deepToString(o));
	}

	public class Pair<K, V> {

		/**
		 * Key of this <code>Pair</code>.
		 */
		private K key;

		/**
		 * Gets the key for this pair.
		 * 
		 * @return key for this pair
		 */
		public K getKey() {
			return key;
		}

		/**
		 * Value of this this <code>Pair</code>.
		 */
		private V value;

		/**
		 * Gets the value for this pair.
		 * 
		 * @return value for this pair
		 */
		public V getValue() {
			return value;
		}

		/**
		 * Creates a new pair
		 * 
		 * @param key   The key for this pair
		 * @param value The value to use for this pair
		 */
		public Pair(K key, V value) {
			this.key = key;
			this.value = value;
		}

		/**
		 * <p>
		 * <code>String</code> representation of this <code>Pair</code>.
		 * </p>
		 *
		 * <p>
		 * The default name/value delimiter '=' is always used.
		 * </p>
		 *
		 * @return <code>String</code> representation of this <code>Pair</code>
		 */
		@Override
		public String toString() {
			return key + "=" + value;
		}

		/**
		 * <p>
		 * Generate a hash code for this <code>Pair</code>.
		 * </p>
		 *
		 * <p>
		 * The hash code is calculated using both the name and the value of the
		 * <code>Pair</code>.
		 * </p>
		 *
		 * @return hash code for this <code>Pair</code>
		 */
		@Override
		public int hashCode() {
			// name's hashCode is multiplied by an arbitrary prime number (13)
			// in order to make sure there is a difference in the hashCode between
			// these two parameters:
			// name: a value: aa
			// name: aa value: a
			return key.hashCode() * 13 + (value == null ? 0 : value.hashCode());
		}

		/**
		 * <p>
		 * Test this <code>Pair</code> for equality with another <code>Object</code>.
		 * </p>
		 *
		 * <p>
		 * If the <code>Object</code> to be tested is not a <code>Pair</code> or is
		 * <code>null</code>, then this method returns <code>false</code>.
		 * </p>
		 *
		 * <p>
		 * Two <code>Pair</code>s are considered equal if and only if both the names and
		 * values are equal.
		 * </p>
		 *
		 * @param o the <code>Object</code> to test for equality with this
		 *          <code>Pair</code>
		 * @return <code>true</code> if the given <code>Object</code> is equal to this
		 *         <code>Pair</code> else <code>false</code>
		 */
		@Override
		public boolean equals(Object o) {
			if (this == o)
				return true;
			if (o instanceof Pair) {
				Pair pair = (Pair) o;
				if (key != null ? !key.equals(pair.key) : pair.key != null)
					return false;
				if (value != null ? !value.equals(pair.value) : pair.value != null)
					return false;
				return true;
			}
			return false;
		}
	}

} Main private static final String NO = "NO"; NO "NO" private static final String YES = "YES"; YES "YES" InputStream is; is PrintWriter out; out String INPUT = ""; INPUT "" private static final long MOD = 1000000007; MOD 1000000007 private static final long inf = 100000000000L; inf 100000000000L private byte[] inbuf = new byte[1024]; inbuf new byte[1024] 1024 public int lenbuf = 0 lenbuf 0 ptrbuf = 0; ptrbuf 0 private boolean vis[]; vis void solve() {
		int T = 1;
		for (int i = 0; i < T; i++)
			solve(i);
	} solve {
		int T = 1;
		for (int i = 0; i < T; i++)
			solve(i);
	} int T = 1; T 1 for (int i = 0; i < T; i++)
			solve(i); int i = 0; int i = 0; i 0 i < T i T i++ i++ i solve(i); solve(i) solve i void solve(int T) {
		long n = nl();
		long sum = 0;
		long p = 1;
		int cnt = 1;
		while (true) {
			p *= 26;
			if (sum + p < n) {
				sum += p;
				cnt++;
			}
			else
				break;
//			tr(sum);
		}
		n-=sum+1;
		char ans[] = new char[cnt];
		for (int i=0; i<cnt; i++) {
			ans[cnt-1-i]=(char) ('a'+n%26);
			n/=26;
		}
		
		out.println(new String(ans));
	} solve {
		long n = nl();
		long sum = 0;
		long p = 1;
		int cnt = 1;
		while (true) {
			p *= 26;
			if (sum + p < n) {
				sum += p;
				cnt++;
			}
			else
				break;
//			tr(sum);
		}
		n-=sum+1;
		char ans[] = new char[cnt];
		for (int i=0; i<cnt; i++) {
			ans[cnt-1-i]=(char) ('a'+n%26);
			n/=26;
		}
		
		out.println(new String(ans));
	} long n = nl(); n nl() nl long sum = 0; sum 0 long p = 1; p 1 int cnt = 1; cnt 1 while (true) {
			p *= 26;
			if (sum + p < n) {
				sum += p;
				cnt++;
			}
			else
				break;
//			tr(sum);
		} true {
			p *= 26;
			if (sum + p < n) {
				sum += p;
				cnt++;
			}
			else
				break;
//			tr(sum);
		} p *= 26 p 26 if (sum + p < n) {
				sum += p;
				cnt++;
			}
			else
				break; sum + p < n sum + p sum p n {
				sum += p;
				cnt++;
			} sum += p sum p cnt++ cnt break; n-=sum+1 n sum+1 sum 1 char ans[] = new char[cnt]; ans new char[cnt] cnt for (int i=0; i<cnt; i++) {
			ans[cnt-1-i]=(char) ('a'+n%26);
			n/=26;
		} int i=0; int i=0; i 0 i<cnt i cnt i++ i++ i {
			ans[cnt-1-i]=(char) ('a'+n%26);
			n/=26;
		} {
			ans[cnt-1-i]=(char) ('a'+n%26);
			n/=26;
		} ans[cnt-1-i]=(char) ('a'+n%26) ans[cnt-1-i] ans cnt-1-i cnt-1-i cnt 1 i (char) ('a'+n%26) 'a' n%26 n 26 n/=26 n 26 out.println(new String(ans)) out.println out new String(ans) int T T // a^b
	long power(long a, long b) {
		long x = 1, y = a;
		while (b > 0) {
			if (b % 2 != 0) {
				x = (x * y) % MOD;
			}
			y = (y * y) % MOD;
			b /= 2;
		}
		return x % MOD;
	} power {
		long x = 1, y = a;
		while (b > 0) {
			if (b % 2 != 0) {
				x = (x * y) % MOD;
			}
			y = (y * y) % MOD;
			b /= 2;
		}
		return x % MOD;
	} long x = 1 x 1 y = a; y a while (b > 0) {
			if (b % 2 != 0) {
				x = (x * y) % MOD;
			}
			y = (y * y) % MOD;
			b /= 2;
		} b > 0 b 0 {
			if (b % 2 != 0) {
				x = (x * y) % MOD;
			}
			y = (y * y) % MOD;
			b /= 2;
		} if (b % 2 != 0) {
				x = (x * y) % MOD;
			} b % 2 != 0 b % 2 b 2 0 {
				x = (x * y) % MOD;
			} x = (x * y) % MOD x (x * y) % MOD (x * y) x y MOD y = (y * y) % MOD y (y * y) % MOD (y * y) y y MOD b /= 2 b 2 return x % MOD; x % MOD x MOD long a a long b b private long gcd(long a, long b) {
		while (a != 0) {
			long tmp = b % a;
			b = a;
			a = tmp;
		}
		return b;
	} gcd {
		while (a != 0) {
			long tmp = b % a;
			b = a;
			a = tmp;
		}
		return b;
	} while (a != 0) {
			long tmp = b % a;
			b = a;
			a = tmp;
		} a != 0 a 0 {
			long tmp = b % a;
			b = a;
			a = tmp;
		} long tmp = b % a; tmp b % a b a b = a b a a = tmp a tmp return b; b long a a long b b void run() throws Exception {
		is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
		out = new PrintWriter(System.out);

		long s = System.currentTimeMillis();
		solve();
		out.flush();
		if (!INPUT.isEmpty())
			tr(System.currentTimeMillis() - s + "ms");
	} run {
		is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
		out = new PrintWriter(System.out);

		long s = System.currentTimeMillis();
		solve();
		out.flush();
		if (!INPUT.isEmpty())
			tr(System.currentTimeMillis() - s + "ms");
	} is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes()) is INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes()) INPUT.isEmpty() INPUT.isEmpty INPUT System.in System System.in new ByteArrayInputStream(INPUT.getBytes()) out = new PrintWriter(System.out) out new PrintWriter(System.out) long s = System.currentTimeMillis(); s System.currentTimeMillis() System.currentTimeMillis System solve() solve out.flush() out.flush out if (!INPUT.isEmpty())
			tr(System.currentTimeMillis() - s + "ms"); !INPUT.isEmpty() INPUT.isEmpty() INPUT.isEmpty INPUT tr(System.currentTimeMillis() - s + "ms") tr System.currentTimeMillis() - s + "ms" System.currentTimeMillis() - s System.currentTimeMillis() System.currentTimeMillis System s "ms" public static void main(String[] args) throws Exception {
		new Main().run();
	} main {
		new Main().run();
	} new Main().run() new Main().run new Main() String[] args args private int readByte() {
		if (lenbuf == -1)
			throw new InputMismatchException();
		if (ptrbuf >= lenbuf) {
			ptrbuf = 0;
			try {
				lenbuf = is.read(inbuf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (lenbuf <= 0)
				return -1;
		}
		return inbuf[ptrbuf++];
	} readByte {
		if (lenbuf == -1)
			throw new InputMismatchException();
		if (ptrbuf >= lenbuf) {
			ptrbuf = 0;
			try {
				lenbuf = is.read(inbuf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (lenbuf <= 0)
				return -1;
		}
		return inbuf[ptrbuf++];
	} if (lenbuf == -1)
			throw new InputMismatchException(); lenbuf == -1 lenbuf -1 1 throw new InputMismatchException(); new InputMismatchException() if (ptrbuf >= lenbuf) {
			ptrbuf = 0;
			try {
				lenbuf = is.read(inbuf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (lenbuf <= 0)
				return -1;
		} ptrbuf >= lenbuf ptrbuf lenbuf {
			ptrbuf = 0;
			try {
				lenbuf = is.read(inbuf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (lenbuf <= 0)
				return -1;
		} ptrbuf = 0 ptrbuf 0 try {
				lenbuf = is.read(inbuf);
			} catch (IOException e) {
				throw new InputMismatchException();
			} catch (IOException e) {
				throw new InputMismatchException();
			} IOException e {
				throw new InputMismatchException();
			} throw new InputMismatchException(); new InputMismatchException() {
				lenbuf = is.read(inbuf);
			} lenbuf = is.read(inbuf) lenbuf is.read(inbuf) is.read is inbuf if (lenbuf <= 0)
				return -1; lenbuf <= 0 lenbuf 0 return -1; -1 1 return inbuf[ptrbuf++]; inbuf[ptrbuf++] inbuf ptrbuf++ ptrbuf private boolean isSpaceChar(int c) {
		return !(c >= 33 && c <= 126);
	} isSpaceChar {
		return !(c >= 33 && c <= 126);
	} return !(c >= 33 && c <= 126); !(c >= 33 && c <= 126) (c >= 33 && c <= 126) c >= 33 c 33 c <= 126 c 126 int c c private int skip() {
		int b;
		while ((b = readByte()) != -1 && isSpaceChar(b))
			;
		return b;
	} skip {
		int b;
		while ((b = readByte()) != -1 && isSpaceChar(b))
			;
		return b;
	} int b; b while ((b = readByte()) != -1 && isSpaceChar(b))
			; (b = readByte()) != -1 && isSpaceChar(b) (b = readByte()) != -1 (b = readByte()) b readByte() readByte -1 1 isSpaceChar(b) isSpaceChar b return b; b private double nd() {
		return Double.parseDouble(ns());
	} nd {
		return Double.parseDouble(ns());
	} return Double.parseDouble(ns()); Double.parseDouble(ns()) Double.parseDouble Double ns() ns private char nc() {
		return (char) skip();
	} nc {
		return (char) skip();
	} return (char) skip(); (char) skip() skip private String ns() {
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while (!(isSpaceChar(b))) { // when nextLine, (isSpaceChar(b) && b != '
									// ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	} ns {
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while (!(isSpaceChar(b))) { // when nextLine, (isSpaceChar(b) && b != '
									// ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	} int b = skip(); b skip() skip StringBuilder sb = new StringBuilder(); sb new StringBuilder() while (!(isSpaceChar(b))) { // when nextLine, (isSpaceChar(b) && b != '
									// ')
			sb.appendCodePoint(b);
			b = readByte();
		} !(isSpaceChar(b)) (isSpaceChar(b)) isSpaceChar b { // when nextLine, (isSpaceChar(b) && b != '
									// ')
			sb.appendCodePoint(b);
			b = readByte();
		} sb.appendCodePoint(b) sb.appendCodePoint sb b b = readByte() b readByte() readByte return sb.toString(); sb.toString() sb.toString sb private char[] ns(int n) {
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while (p < n) {
			if (!(isSpaceChar(b)))
				buf[p++] = (char) b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	} ns {
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while (p < n) {
			if (!(isSpaceChar(b)))
				buf[p++] = (char) b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	} char[] buf = new char[n]; buf new char[n] n int b = skip() b skip() skip p = 0; p 0 while (p < n) {
			if (!(isSpaceChar(b)))
				buf[p++] = (char) b;
			b = readByte();
		} p < n p n {
			if (!(isSpaceChar(b)))
				buf[p++] = (char) b;
			b = readByte();
		} if (!(isSpaceChar(b)))
				buf[p++] = (char) b; !(isSpaceChar(b)) (isSpaceChar(b)) isSpaceChar b buf[p++] = (char) b buf[p++] buf p++ p (char) b b = readByte() b readByte() readByte return n == p ? buf : Arrays.copyOf(buf, p); n == p ? buf : Arrays.copyOf(buf, p) n == p n p buf Arrays.copyOf(buf, p) Arrays.copyOf Arrays buf p int n n private char[][] nm(int n, int m) {
		char[][] map = new char[n][];
		for (int i = 0; i < n; i++)
			map[i] = ns(m);
		return map;
	} nm {
		char[][] map = new char[n][];
		for (int i = 0; i < n; i++)
			map[i] = ns(m);
		return map;
	} char[][] map = new char[n][]; map new char[n][] n for (int i = 0; i < n; i++)
			map[i] = ns(m); int i = 0; int i = 0; i 0 i < n i n i++ i++ i map[i] = ns(m); map[i] = ns(m) map[i] map i ns(m) ns m return map; map int n n int m m private int[] na(int n) {
		int[] a = new int[n];
		for (int i = 0; i < n; i++)
			a[i] = ni();
		return a;
	} na {
		int[] a = new int[n];
		for (int i = 0; i < n; i++)
			a[i] = ni();
		return a;
	} int[] a = new int[n]; a new int[n] n for (int i = 0; i < n; i++)
			a[i] = ni(); int i = 0; int i = 0; i 0 i < n i n i++ i++ i a[i] = ni(); a[i] = ni() a[i] a i ni() ni return a; a int n n private List<Integer> na2(int n) {
		List<Integer> a = new ArrayList<Integer>();
		for (int i = 0; i < n; i++)
			a.add(ni());
		return a;
	} na2 {
		List<Integer> a = new ArrayList<Integer>();
		for (int i = 0; i < n; i++)
			a.add(ni());
		return a;
	} List<Integer> a = new ArrayList<Integer>(); a new ArrayList<Integer>() for (int i = 0; i < n; i++)
			a.add(ni()); int i = 0; int i = 0; i 0 i < n i n i++ i++ i a.add(ni()); a.add(ni()) a.add a ni() ni return a; a int n n private int[][] na(int n, int m) {
		int[][] a = new int[n][];
		for (int i = 0; i < n; i++)
			a[i] = na(m);
		return a;
	} na {
		int[][] a = new int[n][];
		for (int i = 0; i < n; i++)
			a[i] = na(m);
		return a;
	} int[][] a = new int[n][]; a new int[n][] n for (int i = 0; i < n; i++)
			a[i] = na(m); int i = 0; int i = 0; i 0 i < n i n i++ i++ i a[i] = na(m); a[i] = na(m) a[i] a i na(m) na m return a; a int n n int m m private int ni() {
		int num = 0, b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-') {
			minus = true;
			b = readByte();
		}

		while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		}
	} ni {
		int num = 0, b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-') {
			minus = true;
			b = readByte();
		}

		while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		}
	} int num = 0 num 0 b; b boolean minus = false; minus false while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			; (b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-') (b = readByte()) != -1 (b = readByte()) b readByte() readByte -1 1 !((b >= '0' && b <= '9') || b == '-') ((b >= '0' && b <= '9') || b == '-') (b >= '0' && b <= '9') b >= '0' b '0' b <= '9' b '9' b == '-' b '-' if (b == '-') {
			minus = true;
			b = readByte();
		} b == '-' b '-' {
			minus = true;
			b = readByte();
		} minus = true minus true b = readByte() b readByte() readByte while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		} true {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		} if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			} b >= '0' && b <= '9' b >= '0' b '0' b <= '9' b '9' {
				num = num * 10 + (b - '0');
			} num = num * 10 + (b - '0') num num * 10 + (b - '0') num * 10 num 10 (b - '0') b '0' {
				return minus ? -num : num;
			} return minus ? -num : num; minus ? -num : num minus -num num num b = readByte() b readByte() readByte private long[] nl(int n) {
		long[] a = new long[n];
		for (int i = 0; i < n; i++)
			a[i] = nl();
		return a;
	} nl {
		long[] a = new long[n];
		for (int i = 0; i < n; i++)
			a[i] = nl();
		return a;
	} long[] a = new long[n]; a new long[n] n for (int i = 0; i < n; i++)
			a[i] = nl(); int i = 0; int i = 0; i 0 i < n i n i++ i++ i a[i] = nl(); a[i] = nl() a[i] a i nl() nl return a; a int n n private long[][] nl(int n, int m) {
		long[][] a = new long[n][];
		for (int i = 0; i < n; i++)
			a[i] = nl(m);
		return a;
	} nl {
		long[][] a = new long[n][];
		for (int i = 0; i < n; i++)
			a[i] = nl(m);
		return a;
	} long[][] a = new long[n][]; a new long[n][] n for (int i = 0; i < n; i++)
			a[i] = nl(m); int i = 0; int i = 0; i 0 i < n i n i++ i++ i a[i] = nl(m); a[i] = nl(m) a[i] a i nl(m) nl m return a; a int n n int m m private long nl() {
		long num = 0;
		int b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-') {
			minus = true;
			b = readByte();
		}

		while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		}
	} nl {
		long num = 0;
		int b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-') {
			minus = true;
			b = readByte();
		}

		while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		}
	} long num = 0; num 0 int b; b boolean minus = false; minus false while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			; (b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-') (b = readByte()) != -1 (b = readByte()) b readByte() readByte -1 1 !((b >= '0' && b <= '9') || b == '-') ((b >= '0' && b <= '9') || b == '-') (b >= '0' && b <= '9') b >= '0' b '0' b <= '9' b '9' b == '-' b '-' if (b == '-') {
			minus = true;
			b = readByte();
		} b == '-' b '-' {
			minus = true;
			b = readByte();
		} minus = true minus true b = readByte() b readByte() readByte while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		} true {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		} if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			} b >= '0' && b <= '9' b >= '0' b '0' b <= '9' b '9' {
				num = num * 10 + (b - '0');
			} num = num * 10 + (b - '0') num num * 10 + (b - '0') num * 10 num 10 (b - '0') b '0' {
				return minus ? -num : num;
			} return minus ? -num : num; minus ? -num : num minus -num num num b = readByte() b readByte() readByte private static void tr(Object... o) {
		System.out.println(Arrays.deepToString(o));
	} tr {
		System.out.println(Arrays.deepToString(o));
	} System.out.println(Arrays.deepToString(o)) System.out.println System.out System System.out Arrays.deepToString(o) Arrays.deepToString Arrays o Object... o o public class Pair<K, V> {

		/**
		 * Key of this <code>Pair</code>.
		 */
		private K key;

		/**
		 * Gets the key for this pair.
		 * 
		 * @return key for this pair
		 */
		public K getKey() {
			return key;
		}

		/**
		 * Value of this this <code>Pair</code>.
		 */
		private V value;

		/**
		 * Gets the value for this pair.
		 * 
		 * @return value for this pair
		 */
		public V getValue() {
			return value;
		}

		/**
		 * Creates a new pair
		 * 
		 * @param key   The key for this pair
		 * @param value The value to use for this pair
		 */
		public Pair(K key, V value) {
			this.key = key;
			this.value = value;
		}

		/**
		 * <p>
		 * <code>String</code> representation of this <code>Pair</code>.
		 * </p>
		 *
		 * <p>
		 * The default name/value delimiter '=' is always used.
		 * </p>
		 *
		 * @return <code>String</code> representation of this <code>Pair</code>
		 */
		@Override
		public String toString() {
			return key + "=" + value;
		}

		/**
		 * <p>
		 * Generate a hash code for this <code>Pair</code>.
		 * </p>
		 *
		 * <p>
		 * The hash code is calculated using both the name and the value of the
		 * <code>Pair</code>.
		 * </p>
		 *
		 * @return hash code for this <code>Pair</code>
		 */
		@Override
		public int hashCode() {
			// name's hashCode is multiplied by an arbitrary prime number (13)
			// in order to make sure there is a difference in the hashCode between
			// these two parameters:
			// name: a value: aa
			// name: aa value: a
			return key.hashCode() * 13 + (value == null ? 0 : value.hashCode());
		}

		/**
		 * <p>
		 * Test this <code>Pair</code> for equality with another <code>Object</code>.
		 * </p>
		 *
		 * <p>
		 * If the <code>Object</code> to be tested is not a <code>Pair</code> or is
		 * <code>null</code>, then this method returns <code>false</code>.
		 * </p>
		 *
		 * <p>
		 * Two <code>Pair</code>s are considered equal if and only if both the names and
		 * values are equal.
		 * </p>
		 *
		 * @param o the <code>Object</code> to test for equality with this
		 *          <code>Pair</code>
		 * @return <code>true</code> if the given <code>Object</code> is equal to this
		 *         <code>Pair</code> else <code>false</code>
		 */
		@Override
		public boolean equals(Object o) {
			if (this == o)
				return true;
			if (o instanceof Pair) {
				Pair pair = (Pair) o;
				if (key != null ? !key.equals(pair.key) : pair.key != null)
					return false;
				if (value != null ? !value.equals(pair.value) : pair.value != null)
					return false;
				return true;
			}
			return false;
		}
	} Pair /**
		 * Key of this <code>Pair</code>.
		 */
		private K key; key /**
		 * Value of this this <code>Pair</code>.
		 */
		private V value; value /**
		 * Gets the key for this pair.
		 * 
		 * @return key for this pair
		 */
		public K getKey() {
			return key;
		} getKey {
			return key;
		} return key; key /**
		 * Gets the value for this pair.
		 * 
		 * @return value for this pair
		 */
		public V getValue() {
			return value;
		} getValue {
			return value;
		} return value; value /**
		 * Creates a new pair
		 * 
		 * @param key   The key for this pair
		 * @param value The value to use for this pair
		 */
		public Pair(K key, V value) {
			this.key = key;
			this.value = value;
		} Pair {
			this.key = key;
			this.value = value;
		} this.key = key this.key this this.key key this.value = value this.value this this.value value K key key V value value /**
		 * <p>
		 * <code>String</code> representation of this <code>Pair</code>.
		 * </p>
		 *
		 * <p>
		 * The default name/value delimiter '=' is always used.
		 * </p>
		 *
		 * @return <code>String</code> representation of this <code>Pair</code>
		 */
		@Override
		public String toString() {
			return key + "=" + value;
		} toString {
			return key + "=" + value;
		} return key + "=" + value; key + "=" + value key + "=" + value key "=" value /**
		 * <p>
		 * Generate a hash code for this <code>Pair</code>.
		 * </p>
		 *
		 * <p>
		 * The hash code is calculated using both the name and the value of the
		 * <code>Pair</code>.
		 * </p>
		 *
		 * @return hash code for this <code>Pair</code>
		 */
		@Override
		public int hashCode() {
			// name's hashCode is multiplied by an arbitrary prime number (13)
			// in order to make sure there is a difference in the hashCode between
			// these two parameters:
			// name: a value: aa
			// name: aa value: a
			return key.hashCode() * 13 + (value == null ? 0 : value.hashCode());
		} hashCode {
			// name's hashCode is multiplied by an arbitrary prime number (13)
			// in order to make sure there is a difference in the hashCode between
			// these two parameters:
			// name: a value: aa
			// name: aa value: a
			return key.hashCode() * 13 + (value == null ? 0 : value.hashCode());
		} return key.hashCode() * 13 + (value == null ? 0 : value.hashCode()); key.hashCode() * 13 + (value == null ? 0 : value.hashCode()) key.hashCode() * 13 key.hashCode() key.hashCode key 13 (value == null ? 0 : value.hashCode()) value == null value null 0 value.hashCode() value.hashCode value /**
		 * <p>
		 * Test this <code>Pair</code> for equality with another <code>Object</code>.
		 * </p>
		 *
		 * <p>
		 * If the <code>Object</code> to be tested is not a <code>Pair</code> or is
		 * <code>null</code>, then this method returns <code>false</code>.
		 * </p>
		 *
		 * <p>
		 * Two <code>Pair</code>s are considered equal if and only if both the names and
		 * values are equal.
		 * </p>
		 *
		 * @param o the <code>Object</code> to test for equality with this
		 *          <code>Pair</code>
		 * @return <code>true</code> if the given <code>Object</code> is equal to this
		 *         <code>Pair</code> else <code>false</code>
		 */
		@Override
		public boolean equals(Object o) {
			if (this == o)
				return true;
			if (o instanceof Pair) {
				Pair pair = (Pair) o;
				if (key != null ? !key.equals(pair.key) : pair.key != null)
					return false;
				if (value != null ? !value.equals(pair.value) : pair.value != null)
					return false;
				return true;
			}
			return false;
		} equals {
			if (this == o)
				return true;
			if (o instanceof Pair) {
				Pair pair = (Pair) o;
				if (key != null ? !key.equals(pair.key) : pair.key != null)
					return false;
				if (value != null ? !value.equals(pair.value) : pair.value != null)
					return false;
				return true;
			}
			return false;
		} if (this == o)
				return true; this == o this o return true; true if (o instanceof Pair) {
				Pair pair = (Pair) o;
				if (key != null ? !key.equals(pair.key) : pair.key != null)
					return false;
				if (value != null ? !value.equals(pair.value) : pair.value != null)
					return false;
				return true;
			} o instanceof Pair o Pair {
				Pair pair = (Pair) o;
				if (key != null ? !key.equals(pair.key) : pair.key != null)
					return false;
				if (value != null ? !value.equals(pair.value) : pair.value != null)
					return false;
				return true;
			} Pair pair = (Pair) o; pair (Pair) o if (key != null ? !key.equals(pair.key) : pair.key != null)
					return false; key != null ? !key.equals(pair.key) : pair.key != null key != null key null !key.equals(pair.key) key.equals(pair.key) key.equals key pair.key pair pair.key pair.key != null pair.key pair pair.key null return false; false if (value != null ? !value.equals(pair.value) : pair.value != null)
					return false; value != null ? !value.equals(pair.value) : pair.value != null value != null value null !value.equals(pair.value) value.equals(pair.value) value.equals value pair.value pair pair.value pair.value != null pair.value pair pair.value null return false; false return true; true return false; false Object o o public class Main {

	private static final String NO = "NO";
	private static final String YES = "YES";
	InputStream is;
	PrintWriter out;
	String INPUT = "";

	private static final long MOD = 1000000007;
	private static final long inf = 100000000000L;

	void solve() {
		int T = 1;
		for (int i = 0; i < T; i++)
			solve(i);
	}

	void solve(int T) {
		long n = nl();
		long sum = 0;
		long p = 1;
		int cnt = 1;
		while (true) {
			p *= 26;
			if (sum + p < n) {
				sum += p;
				cnt++;
			}
			else
				break;
//			tr(sum);
		}
		n-=sum+1;
		char ans[] = new char[cnt];
		for (int i=0; i<cnt; i++) {
			ans[cnt-1-i]=(char) ('a'+n%26);
			n/=26;
		}
		
		out.println(new String(ans));
	}

	// a^b
	long power(long a, long b) {
		long x = 1, y = a;
		while (b > 0) {
			if (b % 2 != 0) {
				x = (x * y) % MOD;
			}
			y = (y * y) % MOD;
			b /= 2;
		}
		return x % MOD;
	}

	private long gcd(long a, long b) {
		while (a != 0) {
			long tmp = b % a;
			b = a;
			a = tmp;
		}
		return b;
	}

	void run() throws Exception {
		is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
		out = new PrintWriter(System.out);

		long s = System.currentTimeMillis();
		solve();
		out.flush();
		if (!INPUT.isEmpty())
			tr(System.currentTimeMillis() - s + "ms");
	}

	public static void main(String[] args) throws Exception {
		new Main().run();
	}

	private byte[] inbuf = new byte[1024];
	public int lenbuf = 0, ptrbuf = 0;
	private boolean vis[];

	private int readByte() {
		if (lenbuf == -1)
			throw new InputMismatchException();
		if (ptrbuf >= lenbuf) {
			ptrbuf = 0;
			try {
				lenbuf = is.read(inbuf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (lenbuf <= 0)
				return -1;
		}
		return inbuf[ptrbuf++];
	}

	private boolean isSpaceChar(int c) {
		return !(c >= 33 && c <= 126);
	}

	private int skip() {
		int b;
		while ((b = readByte()) != -1 && isSpaceChar(b))
			;
		return b;
	}

	private double nd() {
		return Double.parseDouble(ns());
	}

	private char nc() {
		return (char) skip();
	}

	private String ns() {
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while (!(isSpaceChar(b))) { // when nextLine, (isSpaceChar(b) && b != '
									// ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}

	private char[] ns(int n) {
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while (p < n) {
			if (!(isSpaceChar(b)))
				buf[p++] = (char) b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	}

	private char[][] nm(int n, int m) {
		char[][] map = new char[n][];
		for (int i = 0; i < n; i++)
			map[i] = ns(m);
		return map;
	}

	private int[] na(int n) {
		int[] a = new int[n];
		for (int i = 0; i < n; i++)
			a[i] = ni();
		return a;
	}

	private List<Integer> na2(int n) {
		List<Integer> a = new ArrayList<Integer>();
		for (int i = 0; i < n; i++)
			a.add(ni());
		return a;
	}

	private int[][] na(int n, int m) {
		int[][] a = new int[n][];
		for (int i = 0; i < n; i++)
			a[i] = na(m);
		return a;
	}

	private int ni() {
		int num = 0, b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-') {
			minus = true;
			b = readByte();
		}

		while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		}
	}

	private long[] nl(int n) {
		long[] a = new long[n];
		for (int i = 0; i < n; i++)
			a[i] = nl();
		return a;
	}

	private long[][] nl(int n, int m) {
		long[][] a = new long[n][];
		for (int i = 0; i < n; i++)
			a[i] = nl(m);
		return a;
	}

	private long nl() {
		long num = 0;
		int b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-') {
			minus = true;
			b = readByte();
		}

		while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		}
	}

	private static void tr(Object... o) {
		System.out.println(Arrays.deepToString(o));
	}

	public class Pair<K, V> {

		/**
		 * Key of this <code>Pair</code>.
		 */
		private K key;

		/**
		 * Gets the key for this pair.
		 * 
		 * @return key for this pair
		 */
		public K getKey() {
			return key;
		}

		/**
		 * Value of this this <code>Pair</code>.
		 */
		private V value;

		/**
		 * Gets the value for this pair.
		 * 
		 * @return value for this pair
		 */
		public V getValue() {
			return value;
		}

		/**
		 * Creates a new pair
		 * 
		 * @param key   The key for this pair
		 * @param value The value to use for this pair
		 */
		public Pair(K key, V value) {
			this.key = key;
			this.value = value;
		}

		/**
		 * <p>
		 * <code>String</code> representation of this <code>Pair</code>.
		 * </p>
		 *
		 * <p>
		 * The default name/value delimiter '=' is always used.
		 * </p>
		 *
		 * @return <code>String</code> representation of this <code>Pair</code>
		 */
		@Override
		public String toString() {
			return key + "=" + value;
		}

		/**
		 * <p>
		 * Generate a hash code for this <code>Pair</code>.
		 * </p>
		 *
		 * <p>
		 * The hash code is calculated using both the name and the value of the
		 * <code>Pair</code>.
		 * </p>
		 *
		 * @return hash code for this <code>Pair</code>
		 */
		@Override
		public int hashCode() {
			// name's hashCode is multiplied by an arbitrary prime number (13)
			// in order to make sure there is a difference in the hashCode between
			// these two parameters:
			// name: a value: aa
			// name: aa value: a
			return key.hashCode() * 13 + (value == null ? 0 : value.hashCode());
		}

		/**
		 * <p>
		 * Test this <code>Pair</code> for equality with another <code>Object</code>.
		 * </p>
		 *
		 * <p>
		 * If the <code>Object</code> to be tested is not a <code>Pair</code> or is
		 * <code>null</code>, then this method returns <code>false</code>.
		 * </p>
		 *
		 * <p>
		 * Two <code>Pair</code>s are considered equal if and only if both the names and
		 * values are equal.
		 * </p>
		 *
		 * @param o the <code>Object</code> to test for equality with this
		 *          <code>Pair</code>
		 * @return <code>true</code> if the given <code>Object</code> is equal to this
		 *         <code>Pair</code> else <code>false</code>
		 */
		@Override
		public boolean equals(Object o) {
			if (this == o)
				return true;
			if (o instanceof Pair) {
				Pair pair = (Pair) o;
				if (key != null ? !key.equals(pair.key) : pair.key != null)
					return false;
				if (value != null ? !value.equals(pair.value) : pair.value != null)
					return false;
				return true;
			}
			return false;
		}
	}

} public class Main {

	private static final String NO = "NO";
	private static final String YES = "YES";
	InputStream is;
	PrintWriter out;
	String INPUT = "";

	private static final long MOD = 1000000007;
	private static final long inf = 100000000000L;

	void solve() {
		int T = 1;
		for (int i = 0; i < T; i++)
			solve(i);
	}

	void solve(int T) {
		long n = nl();
		long sum = 0;
		long p = 1;
		int cnt = 1;
		while (true) {
			p *= 26;
			if (sum + p < n) {
				sum += p;
				cnt++;
			}
			else
				break;
//			tr(sum);
		}
		n-=sum+1;
		char ans[] = new char[cnt];
		for (int i=0; i<cnt; i++) {
			ans[cnt-1-i]=(char) ('a'+n%26);
			n/=26;
		}
		
		out.println(new String(ans));
	}

	// a^b
	long power(long a, long b) {
		long x = 1, y = a;
		while (b > 0) {
			if (b % 2 != 0) {
				x = (x * y) % MOD;
			}
			y = (y * y) % MOD;
			b /= 2;
		}
		return x % MOD;
	}

	private long gcd(long a, long b) {
		while (a != 0) {
			long tmp = b % a;
			b = a;
			a = tmp;
		}
		return b;
	}

	void run() throws Exception {
		is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
		out = new PrintWriter(System.out);

		long s = System.currentTimeMillis();
		solve();
		out.flush();
		if (!INPUT.isEmpty())
			tr(System.currentTimeMillis() - s + "ms");
	}

	public static void main(String[] args) throws Exception {
		new Main().run();
	}

	private byte[] inbuf = new byte[1024];
	public int lenbuf = 0, ptrbuf = 0;
	private boolean vis[];

	private int readByte() {
		if (lenbuf == -1)
			throw new InputMismatchException();
		if (ptrbuf >= lenbuf) {
			ptrbuf = 0;
			try {
				lenbuf = is.read(inbuf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (lenbuf <= 0)
				return -1;
		}
		return inbuf[ptrbuf++];
	}

	private boolean isSpaceChar(int c) {
		return !(c >= 33 && c <= 126);
	}

	private int skip() {
		int b;
		while ((b = readByte()) != -1 && isSpaceChar(b))
			;
		return b;
	}

	private double nd() {
		return Double.parseDouble(ns());
	}

	private char nc() {
		return (char) skip();
	}

	private String ns() {
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while (!(isSpaceChar(b))) { // when nextLine, (isSpaceChar(b) && b != '
									// ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}

	private char[] ns(int n) {
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while (p < n) {
			if (!(isSpaceChar(b)))
				buf[p++] = (char) b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	}

	private char[][] nm(int n, int m) {
		char[][] map = new char[n][];
		for (int i = 0; i < n; i++)
			map[i] = ns(m);
		return map;
	}

	private int[] na(int n) {
		int[] a = new int[n];
		for (int i = 0; i < n; i++)
			a[i] = ni();
		return a;
	}

	private List<Integer> na2(int n) {
		List<Integer> a = new ArrayList<Integer>();
		for (int i = 0; i < n; i++)
			a.add(ni());
		return a;
	}

	private int[][] na(int n, int m) {
		int[][] a = new int[n][];
		for (int i = 0; i < n; i++)
			a[i] = na(m);
		return a;
	}

	private int ni() {
		int num = 0, b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-') {
			minus = true;
			b = readByte();
		}

		while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		}
	}

	private long[] nl(int n) {
		long[] a = new long[n];
		for (int i = 0; i < n; i++)
			a[i] = nl();
		return a;
	}

	private long[][] nl(int n, int m) {
		long[][] a = new long[n][];
		for (int i = 0; i < n; i++)
			a[i] = nl(m);
		return a;
	}

	private long nl() {
		long num = 0;
		int b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-') {
			minus = true;
			b = readByte();
		}

		while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		}
	}

	private static void tr(Object... o) {
		System.out.println(Arrays.deepToString(o));
	}

	public class Pair<K, V> {

		/**
		 * Key of this <code>Pair</code>.
		 */
		private K key;

		/**
		 * Gets the key for this pair.
		 * 
		 * @return key for this pair
		 */
		public K getKey() {
			return key;
		}

		/**
		 * Value of this this <code>Pair</code>.
		 */
		private V value;

		/**
		 * Gets the value for this pair.
		 * 
		 * @return value for this pair
		 */
		public V getValue() {
			return value;
		}

		/**
		 * Creates a new pair
		 * 
		 * @param key   The key for this pair
		 * @param value The value to use for this pair
		 */
		public Pair(K key, V value) {
			this.key = key;
			this.value = value;
		}

		/**
		 * <p>
		 * <code>String</code> representation of this <code>Pair</code>.
		 * </p>
		 *
		 * <p>
		 * The default name/value delimiter '=' is always used.
		 * </p>
		 *
		 * @return <code>String</code> representation of this <code>Pair</code>
		 */
		@Override
		public String toString() {
			return key + "=" + value;
		}

		/**
		 * <p>
		 * Generate a hash code for this <code>Pair</code>.
		 * </p>
		 *
		 * <p>
		 * The hash code is calculated using both the name and the value of the
		 * <code>Pair</code>.
		 * </p>
		 *
		 * @return hash code for this <code>Pair</code>
		 */
		@Override
		public int hashCode() {
			// name's hashCode is multiplied by an arbitrary prime number (13)
			// in order to make sure there is a difference in the hashCode between
			// these two parameters:
			// name: a value: aa
			// name: aa value: a
			return key.hashCode() * 13 + (value == null ? 0 : value.hashCode());
		}

		/**
		 * <p>
		 * Test this <code>Pair</code> for equality with another <code>Object</code>.
		 * </p>
		 *
		 * <p>
		 * If the <code>Object</code> to be tested is not a <code>Pair</code> or is
		 * <code>null</code>, then this method returns <code>false</code>.
		 * </p>
		 *
		 * <p>
		 * Two <code>Pair</code>s are considered equal if and only if both the names and
		 * values are equal.
		 * </p>
		 *
		 * @param o the <code>Object</code> to test for equality with this
		 *          <code>Pair</code>
		 * @return <code>true</code> if the given <code>Object</code> is equal to this
		 *         <code>Pair</code> else <code>false</code>
		 */
		@Override
		public boolean equals(Object o) {
			if (this == o)
				return true;
			if (o instanceof Pair) {
				Pair pair = (Pair) o;
				if (key != null ? !key.equals(pair.key) : pair.key != null)
					return false;
				if (value != null ? !value.equals(pair.value) : pair.value != null)
					return false;
				return true;
			}
			return false;
		}
	}

} Main
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.InputMismatchException;
import java.util.List;
import java.util.Map;

public class Main {

	private static final String NO = "NO";
	private static final String YES = "YES";
	InputStream is;
	PrintWriter out;
	String INPUT = "";

	private static final long MOD = 1000000007;
	private static final long inf = 100000000000L;

	void solve() {
		int T = 1;
		for (int i = 0; i < T; i++)
			solve(i);
	}

	void solve(int T) {
		long n = nl();
		long sum = 0;
		long p = 1;
		int cnt = 1;
		while (true) {
			p *= 26;
			if (sum + p < n) {
				sum += p;
				cnt++;
			}
			else
				break;
//			tr(sum);
		}
		n-=sum+1;
		char ans[] = new char[cnt];
		for (int i=0; i<cnt; i++) {
			ans[cnt-1-i]=(char) ('a'+n%26);
			n/=26;
		}
		
		out.println(new String(ans));
	}

	// a^b
	long power(long a, long b) {
		long x = 1, y = a;
		while (b > 0) {
			if (b % 2 != 0) {
				x = (x * y) % MOD;
			}
			y = (y * y) % MOD;
			b /= 2;
		}
		return x % MOD;
	}

	private long gcd(long a, long b) {
		while (a != 0) {
			long tmp = b % a;
			b = a;
			a = tmp;
		}
		return b;
	}

	void run() throws Exception {
		is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
		out = new PrintWriter(System.out);

		long s = System.currentTimeMillis();
		solve();
		out.flush();
		if (!INPUT.isEmpty())
			tr(System.currentTimeMillis() - s + "ms");
	}

	public static void main(String[] args) throws Exception {
		new Main().run();
	}

	private byte[] inbuf = new byte[1024];
	public int lenbuf = 0, ptrbuf = 0;
	private boolean vis[];

	private int readByte() {
		if (lenbuf == -1)
			throw new InputMismatchException();
		if (ptrbuf >= lenbuf) {
			ptrbuf = 0;
			try {
				lenbuf = is.read(inbuf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (lenbuf <= 0)
				return -1;
		}
		return inbuf[ptrbuf++];
	}

	private boolean isSpaceChar(int c) {
		return !(c >= 33 && c <= 126);
	}

	private int skip() {
		int b;
		while ((b = readByte()) != -1 && isSpaceChar(b))
			;
		return b;
	}

	private double nd() {
		return Double.parseDouble(ns());
	}

	private char nc() {
		return (char) skip();
	}

	private String ns() {
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while (!(isSpaceChar(b))) { // when nextLine, (isSpaceChar(b) && b != '
									// ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}

	private char[] ns(int n) {
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while (p < n) {
			if (!(isSpaceChar(b)))
				buf[p++] = (char) b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	}

	private char[][] nm(int n, int m) {
		char[][] map = new char[n][];
		for (int i = 0; i < n; i++)
			map[i] = ns(m);
		return map;
	}

	private int[] na(int n) {
		int[] a = new int[n];
		for (int i = 0; i < n; i++)
			a[i] = ni();
		return a;
	}

	private List<Integer> na2(int n) {
		List<Integer> a = new ArrayList<Integer>();
		for (int i = 0; i < n; i++)
			a.add(ni());
		return a;
	}

	private int[][] na(int n, int m) {
		int[][] a = new int[n][];
		for (int i = 0; i < n; i++)
			a[i] = na(m);
		return a;
	}

	private int ni() {
		int num = 0, b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-') {
			minus = true;
			b = readByte();
		}

		while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		}
	}

	private long[] nl(int n) {
		long[] a = new long[n];
		for (int i = 0; i < n; i++)
			a[i] = nl();
		return a;
	}

	private long[][] nl(int n, int m) {
		long[][] a = new long[n][];
		for (int i = 0; i < n; i++)
			a[i] = nl(m);
		return a;
	}

	private long nl() {
		long num = 0;
		int b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-') {
			minus = true;
			b = readByte();
		}

		while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		}
	}

	private static void tr(Object... o) {
		System.out.println(Arrays.deepToString(o));
	}

	public class Pair<K, V> {

		/**
		 * Key of this <code>Pair</code>.
		 */
		private K key;

		/**
		 * Gets the key for this pair.
		 * 
		 * @return key for this pair
		 */
		public K getKey() {
			return key;
		}

		/**
		 * Value of this this <code>Pair</code>.
		 */
		private V value;

		/**
		 * Gets the value for this pair.
		 * 
		 * @return value for this pair
		 */
		public V getValue() {
			return value;
		}

		/**
		 * Creates a new pair
		 * 
		 * @param key   The key for this pair
		 * @param value The value to use for this pair
		 */
		public Pair(K key, V value) {
			this.key = key;
			this.value = value;
		}

		/**
		 * <p>
		 * <code>String</code> representation of this <code>Pair</code>.
		 * </p>
		 *
		 * <p>
		 * The default name/value delimiter '=' is always used.
		 * </p>
		 *
		 * @return <code>String</code> representation of this <code>Pair</code>
		 */
		@Override
		public String toString() {
			return key + "=" + value;
		}

		/**
		 * <p>
		 * Generate a hash code for this <code>Pair</code>.
		 * </p>
		 *
		 * <p>
		 * The hash code is calculated using both the name and the value of the
		 * <code>Pair</code>.
		 * </p>
		 *
		 * @return hash code for this <code>Pair</code>
		 */
		@Override
		public int hashCode() {
			// name's hashCode is multiplied by an arbitrary prime number (13)
			// in order to make sure there is a difference in the hashCode between
			// these two parameters:
			// name: a value: aa
			// name: aa value: a
			return key.hashCode() * 13 + (value == null ? 0 : value.hashCode());
		}

		/**
		 * <p>
		 * Test this <code>Pair</code> for equality with another <code>Object</code>.
		 * </p>
		 *
		 * <p>
		 * If the <code>Object</code> to be tested is not a <code>Pair</code> or is
		 * <code>null</code>, then this method returns <code>false</code>.
		 * </p>
		 *
		 * <p>
		 * Two <code>Pair</code>s are considered equal if and only if both the names and
		 * values are equal.
		 * </p>
		 *
		 * @param o the <code>Object</code> to test for equality with this
		 *          <code>Pair</code>
		 * @return <code>true</code> if the given <code>Object</code> is equal to this
		 *         <code>Pair</code> else <code>false</code>
		 */
		@Override
		public boolean equals(Object o) {
			if (this == o)
				return true;
			if (o instanceof Pair) {
				Pair pair = (Pair) o;
				if (key != null ? !key.equals(pair.key) : pair.key != null)
					return false;
				if (value != null ? !value.equals(pair.value) : pair.value != null)
					return false;
				return true;
			}
			return false;
		}
	}

}