import java.util.*;
public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);

		long n = sc.nextLong();

		int k = 1;
		long z = 26L;
		long d = 0L;
		while ( z < n ) {
			d = z;
			k++;
			z += (long)Math.pow(26, k);
		}

		long y = n - d - 1L;
		String alp = "abcdefghijklmnopqrstuvwxyz";

		String[] s = new String[k];
		for ( int i=k-1; i>=0; i-- ) {
			int c = (int)(y%26L);
			s[i] = alp.substring(c, c+1);

			y = y/26L;
		}
		System.out.println(String.join("", s));

	}
} import java.util.*; util.* java public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);

		long n = sc.nextLong();

		int k = 1;
		long z = 26L;
		long d = 0L;
		while ( z < n ) {
			d = z;
			k++;
			z += (long)Math.pow(26, k);
		}

		long y = n - d - 1L;
		String alp = "abcdefghijklmnopqrstuvwxyz";

		String[] s = new String[k];
		for ( int i=k-1; i>=0; i-- ) {
			int c = (int)(y%26L);
			s[i] = alp.substring(c, c+1);

			y = y/26L;
		}
		System.out.println(String.join("", s));

	}
} Main public static void main(String[] args){
		Scanner sc = new Scanner(System.in);

		long n = sc.nextLong();

		int k = 1;
		long z = 26L;
		long d = 0L;
		while ( z < n ) {
			d = z;
			k++;
			z += (long)Math.pow(26, k);
		}

		long y = n - d - 1L;
		String alp = "abcdefghijklmnopqrstuvwxyz";

		String[] s = new String[k];
		for ( int i=k-1; i>=0; i-- ) {
			int c = (int)(y%26L);
			s[i] = alp.substring(c, c+1);

			y = y/26L;
		}
		System.out.println(String.join("", s));

	} main {
		Scanner sc = new Scanner(System.in);

		long n = sc.nextLong();

		int k = 1;
		long z = 26L;
		long d = 0L;
		while ( z < n ) {
			d = z;
			k++;
			z += (long)Math.pow(26, k);
		}

		long y = n - d - 1L;
		String alp = "abcdefghijklmnopqrstuvwxyz";

		String[] s = new String[k];
		for ( int i=k-1; i>=0; i-- ) {
			int c = (int)(y%26L);
			s[i] = alp.substring(c, c+1);

			y = y/26L;
		}
		System.out.println(String.join("", s));

	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long n = sc.nextLong(); n sc.nextLong() sc.nextLong sc int k = 1; k 1 long z = 26L; z 26L long d = 0L; d 0L while ( z < n ) {
			d = z;
			k++;
			z += (long)Math.pow(26, k);
		} z < n z n {
			d = z;
			k++;
			z += (long)Math.pow(26, k);
		} d = z d z k++ k z += (long)Math.pow(26, k) z (long)Math.pow(26, k) Math.pow Math 26 k long y = n - d - 1L; y n - d - 1L n - d - 1L n d 1L String alp = "abcdefghijklmnopqrstuvwxyz"; alp "abcdefghijklmnopqrstuvwxyz" String[] s = new String[k]; s new String[k] k for ( int i=k-1; i>=0; i-- ) {
			int c = (int)(y%26L);
			s[i] = alp.substring(c, c+1);

			y = y/26L;
		} int i=k-1; int i=k-1; i k-1 k 1 i>=0 i 0 i-- i-- i {
			int c = (int)(y%26L);
			s[i] = alp.substring(c, c+1);

			y = y/26L;
		} {
			int c = (int)(y%26L);
			s[i] = alp.substring(c, c+1);

			y = y/26L;
		} int c = (int)(y%26L); c (int)(y%26L) y 26L s[i] = alp.substring(c, c+1) s[i] s i alp.substring(c, c+1) alp.substring alp c c+1 c 1 y = y/26L y y/26L y 26L System.out.println(String.join("", s)) System.out.println System.out System System.out String.join("", s) String.join String "" s String[] args args public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);

		long n = sc.nextLong();

		int k = 1;
		long z = 26L;
		long d = 0L;
		while ( z < n ) {
			d = z;
			k++;
			z += (long)Math.pow(26, k);
		}

		long y = n - d - 1L;
		String alp = "abcdefghijklmnopqrstuvwxyz";

		String[] s = new String[k];
		for ( int i=k-1; i>=0; i-- ) {
			int c = (int)(y%26L);
			s[i] = alp.substring(c, c+1);

			y = y/26L;
		}
		System.out.println(String.join("", s));

	}
} public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);

		long n = sc.nextLong();

		int k = 1;
		long z = 26L;
		long d = 0L;
		while ( z < n ) {
			d = z;
			k++;
			z += (long)Math.pow(26, k);
		}

		long y = n - d - 1L;
		String alp = "abcdefghijklmnopqrstuvwxyz";

		String[] s = new String[k];
		for ( int i=k-1; i>=0; i-- ) {
			int c = (int)(y%26L);
			s[i] = alp.substring(c, c+1);

			y = y/26L;
		}
		System.out.println(String.join("", s));

	}
} Main
import java.util.*;
public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);

		long n = sc.nextLong();

		int k = 1;
		long z = 26L;
		long d = 0L;
		while ( z < n ) {
			d = z;
			k++;
			z += (long)Math.pow(26, k);
		}

		long y = n - d - 1L;
		String alp = "abcdefghijklmnopqrstuvwxyz";

		String[] s = new String[k];
		for ( int i=k-1; i>=0; i-- ) {
			int c = (int)(y%26L);
			s[i] = alp.substring(c, c+1);

			y = y/26L;
		}
		System.out.println(String.join("", s));

	}
}
