import java.util.*;
import java.io.*;
import java.math.*;
 
public class Main {
    static PrintWriter out = new PrintWriter(System.out);
    static Reader in = new Reader();
    public static void main(String[] args) throws IOException {
        Main solver = new Main();
        solver.solve();
        out.flush();
        out.close();
 
    }
 
    static int INF = (int)1e9;
    static int maxn = (int)2e4+5;
    static int mod  = 1000*1000*1000+7;
    static int n,m,q,k,t;
    
    void solve() throws IOException{
        long len = in.nextLong();
        
        long[] p = new long[15];
        p[0] = 1;
        for (int i = 1; i < 15; i++) p[i] = p[i-1]*26L;
        
        StringBuilder ans = new StringBuilder("");
        long cur = 1, cnt = 1;
        while (len != 0) {
            cnt*=26L;
            
            if (cnt < len) { 
                len -= cnt;
                cur++;
            } else {
                for (int i = 0; i < cur; i++) {
                    for (int j = 0; j < 26; j++) {
                        if (len-p[(int)cur-i-1] > 0) {
                            len -= p[(int)cur-i-1];
                            continue;
                        } else {
                            ans.append((char)(j+'a')+"");
                            break;
                        }
                    }
                }
                len = 0;
            }
        }
        out.println(ans);
    }
    
    //<>
    
    
    static class Reader {
 
    private InputStream mIs;
    private byte[] buf = new byte[1024];
    private int curChar;
    private int numChars;
 
    public Reader() {
        this(System.in);
    }
 
    public Reader(InputStream is) {
        mIs = is;
    }
 
    public int read() {
        if (numChars == -1) {
            throw new InputMismatchException();
 
    }
        if (curChar >= numChars) {
            curChar = 0;
            try {
                numChars = mIs.read(buf);
            } catch (IOException e) {
                throw new InputMismatchException();
            }
            if (numChars <= 0) {
                return -1;
            }
        }
        return buf[curChar++];
    }
 
    public String nextLine() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(c);
            c = read();
        } while (!isEndOfLine(c));
        return res.toString();
    }
 
    public String next() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(c);
            c = read();
        } while (!isSpaceChar(c));
        return res.toString();
    }
 
    double nextDouble()
    {
        return Double.parseDouble(next());
    }
 
    public long nextLong() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        long res = 0;
        do {
            if (c < '0' || c > '9') {
                throw new InputMismatchException();
            }
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    }
 
    public int nextInt() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        int res = 0;
        do {
            if (c < '0' || c > '9') {
                throw new InputMismatchException();
            }
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    }
 
    public boolean isSpaceChar(int c) {
        return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
    }
 
    public boolean isEndOfLine(int c) {
        return c == '\n' || c == '\r' || c == -1;
    }
 
    }
} import java.util.*; util.* java import java.io.*; io.* java import java.math.*; math.* java public class Main {
    static PrintWriter out = new PrintWriter(System.out);
    static Reader in = new Reader();
    public static void main(String[] args) throws IOException {
        Main solver = new Main();
        solver.solve();
        out.flush();
        out.close();
 
    }
 
    static int INF = (int)1e9;
    static int maxn = (int)2e4+5;
    static int mod  = 1000*1000*1000+7;
    static int n,m,q,k,t;
    
    void solve() throws IOException{
        long len = in.nextLong();
        
        long[] p = new long[15];
        p[0] = 1;
        for (int i = 1; i < 15; i++) p[i] = p[i-1]*26L;
        
        StringBuilder ans = new StringBuilder("");
        long cur = 1, cnt = 1;
        while (len != 0) {
            cnt*=26L;
            
            if (cnt < len) { 
                len -= cnt;
                cur++;
            } else {
                for (int i = 0; i < cur; i++) {
                    for (int j = 0; j < 26; j++) {
                        if (len-p[(int)cur-i-1] > 0) {
                            len -= p[(int)cur-i-1];
                            continue;
                        } else {
                            ans.append((char)(j+'a')+"");
                            break;
                        }
                    }
                }
                len = 0;
            }
        }
        out.println(ans);
    }
    
    //<>
    
    
    static class Reader {
 
    private InputStream mIs;
    private byte[] buf = new byte[1024];
    private int curChar;
    private int numChars;
 
    public Reader() {
        this(System.in);
    }
 
    public Reader(InputStream is) {
        mIs = is;
    }
 
    public int read() {
        if (numChars == -1) {
            throw new InputMismatchException();
 
    }
        if (curChar >= numChars) {
            curChar = 0;
            try {
                numChars = mIs.read(buf);
            } catch (IOException e) {
                throw new InputMismatchException();
            }
            if (numChars <= 0) {
                return -1;
            }
        }
        return buf[curChar++];
    }
 
    public String nextLine() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(c);
            c = read();
        } while (!isEndOfLine(c));
        return res.toString();
    }
 
    public String next() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(c);
            c = read();
        } while (!isSpaceChar(c));
        return res.toString();
    }
 
    double nextDouble()
    {
        return Double.parseDouble(next());
    }
 
    public long nextLong() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        long res = 0;
        do {
            if (c < '0' || c > '9') {
                throw new InputMismatchException();
            }
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    }
 
    public int nextInt() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        int res = 0;
        do {
            if (c < '0' || c > '9') {
                throw new InputMismatchException();
            }
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    }
 
    public boolean isSpaceChar(int c) {
        return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
    }
 
    public boolean isEndOfLine(int c) {
        return c == '\n' || c == '\r' || c == -1;
    }
 
    }
} Main static PrintWriter out = new PrintWriter(System.out); out new PrintWriter(System.out) static Reader in = new Reader(); in new Reader() static int INF = (int)1e9; INF (int)1e9 static int maxn = (int)2e4+5; maxn (int)2e4+5 (int)2e4 5 static int mod  = 1000*1000*1000+7; mod 1000*1000*1000+7 1000*1000*1000 1000*1000*1000 1000 1000 1000 7 static int n n m m q q k k t; t public static void main(String[] args) throws IOException {
        Main solver = new Main();
        solver.solve();
        out.flush();
        out.close();
 
    } main {
        Main solver = new Main();
        solver.solve();
        out.flush();
        out.close();
 
    } Main solver = new Main(); solver new Main() solver.solve() solver.solve solver out.flush() out.flush out out.close() out.close out String[] args args void solve() throws IOException{
        long len = in.nextLong();
        
        long[] p = new long[15];
        p[0] = 1;
        for (int i = 1; i < 15; i++) p[i] = p[i-1]*26L;
        
        StringBuilder ans = new StringBuilder("");
        long cur = 1, cnt = 1;
        while (len != 0) {
            cnt*=26L;
            
            if (cnt < len) { 
                len -= cnt;
                cur++;
            } else {
                for (int i = 0; i < cur; i++) {
                    for (int j = 0; j < 26; j++) {
                        if (len-p[(int)cur-i-1] > 0) {
                            len -= p[(int)cur-i-1];
                            continue;
                        } else {
                            ans.append((char)(j+'a')+"");
                            break;
                        }
                    }
                }
                len = 0;
            }
        }
        out.println(ans);
    } solve {
        long len = in.nextLong();
        
        long[] p = new long[15];
        p[0] = 1;
        for (int i = 1; i < 15; i++) p[i] = p[i-1]*26L;
        
        StringBuilder ans = new StringBuilder("");
        long cur = 1, cnt = 1;
        while (len != 0) {
            cnt*=26L;
            
            if (cnt < len) { 
                len -= cnt;
                cur++;
            } else {
                for (int i = 0; i < cur; i++) {
                    for (int j = 0; j < 26; j++) {
                        if (len-p[(int)cur-i-1] > 0) {
                            len -= p[(int)cur-i-1];
                            continue;
                        } else {
                            ans.append((char)(j+'a')+"");
                            break;
                        }
                    }
                }
                len = 0;
            }
        }
        out.println(ans);
    } long len = in.nextLong(); len in.nextLong() in.nextLong in long[] p = new long[15]; p new long[15] 15 p[0] = 1 p[0] p 0 1 for (int i = 1; i < 15; i++) p[i] = p[i-1]*26L; int i = 1; int i = 1; i 1 i < 15 i 15 i++ i++ i p[i] = p[i-1]*26L; p[i] = p[i-1]*26L p[i] p i p[i-1]*26L p[i-1] p i-1 i 1 26L StringBuilder ans = new StringBuilder(""); ans new StringBuilder("") long cur = 1 cur 1 cnt = 1; cnt 1 while (len != 0) {
            cnt*=26L;
            
            if (cnt < len) { 
                len -= cnt;
                cur++;
            } else {
                for (int i = 0; i < cur; i++) {
                    for (int j = 0; j < 26; j++) {
                        if (len-p[(int)cur-i-1] > 0) {
                            len -= p[(int)cur-i-1];
                            continue;
                        } else {
                            ans.append((char)(j+'a')+"");
                            break;
                        }
                    }
                }
                len = 0;
            }
        } len != 0 len 0 {
            cnt*=26L;
            
            if (cnt < len) { 
                len -= cnt;
                cur++;
            } else {
                for (int i = 0; i < cur; i++) {
                    for (int j = 0; j < 26; j++) {
                        if (len-p[(int)cur-i-1] > 0) {
                            len -= p[(int)cur-i-1];
                            continue;
                        } else {
                            ans.append((char)(j+'a')+"");
                            break;
                        }
                    }
                }
                len = 0;
            }
        } cnt*=26L cnt 26L if (cnt < len) { 
                len -= cnt;
                cur++;
            } else {
                for (int i = 0; i < cur; i++) {
                    for (int j = 0; j < 26; j++) {
                        if (len-p[(int)cur-i-1] > 0) {
                            len -= p[(int)cur-i-1];
                            continue;
                        } else {
                            ans.append((char)(j+'a')+"");
                            break;
                        }
                    }
                }
                len = 0;
            } cnt < len cnt len { 
                len -= cnt;
                cur++;
            } len -= cnt len cnt cur++ cur {
                for (int i = 0; i < cur; i++) {
                    for (int j = 0; j < 26; j++) {
                        if (len-p[(int)cur-i-1] > 0) {
                            len -= p[(int)cur-i-1];
                            continue;
                        } else {
                            ans.append((char)(j+'a')+"");
                            break;
                        }
                    }
                }
                len = 0;
            } for (int i = 0; i < cur; i++) {
                    for (int j = 0; j < 26; j++) {
                        if (len-p[(int)cur-i-1] > 0) {
                            len -= p[(int)cur-i-1];
                            continue;
                        } else {
                            ans.append((char)(j+'a')+"");
                            break;
                        }
                    }
                } int i = 0; int i = 0; i 0 i < cur i cur i++ i++ i {
                    for (int j = 0; j < 26; j++) {
                        if (len-p[(int)cur-i-1] > 0) {
                            len -= p[(int)cur-i-1];
                            continue;
                        } else {
                            ans.append((char)(j+'a')+"");
                            break;
                        }
                    }
                } {
                    for (int j = 0; j < 26; j++) {
                        if (len-p[(int)cur-i-1] > 0) {
                            len -= p[(int)cur-i-1];
                            continue;
                        } else {
                            ans.append((char)(j+'a')+"");
                            break;
                        }
                    }
                } for (int j = 0; j < 26; j++) {
                        if (len-p[(int)cur-i-1] > 0) {
                            len -= p[(int)cur-i-1];
                            continue;
                        } else {
                            ans.append((char)(j+'a')+"");
                            break;
                        }
                    } int j = 0; int j = 0; j 0 j < 26 j 26 j++ j++ j {
                        if (len-p[(int)cur-i-1] > 0) {
                            len -= p[(int)cur-i-1];
                            continue;
                        } else {
                            ans.append((char)(j+'a')+"");
                            break;
                        }
                    } {
                        if (len-p[(int)cur-i-1] > 0) {
                            len -= p[(int)cur-i-1];
                            continue;
                        } else {
                            ans.append((char)(j+'a')+"");
                            break;
                        }
                    } if (len-p[(int)cur-i-1] > 0) {
                            len -= p[(int)cur-i-1];
                            continue;
                        } else {
                            ans.append((char)(j+'a')+"");
                            break;
                        } len-p[(int)cur-i-1] > 0 len-p[(int)cur-i-1] len p[(int)cur-i-1] p (int)cur-i-1 (int)cur-i-1 (int)cur i 1 0 {
                            len -= p[(int)cur-i-1];
                            continue;
                        } len -= p[(int)cur-i-1] len p[(int)cur-i-1] p (int)cur-i-1 (int)cur-i-1 (int)cur i 1 continue; {
                            ans.append((char)(j+'a')+"");
                            break;
                        } ans.append((char)(j+'a')+"") ans.append ans (char)(j+'a')+"" (char)(j+'a') j 'a' "" break; len = 0 len 0 out.println(ans) out.println out ans static class Reader {
 
    private InputStream mIs;
    private byte[] buf = new byte[1024];
    private int curChar;
    private int numChars;
 
    public Reader() {
        this(System.in);
    }
 
    public Reader(InputStream is) {
        mIs = is;
    }
 
    public int read() {
        if (numChars == -1) {
            throw new InputMismatchException();
 
    }
        if (curChar >= numChars) {
            curChar = 0;
            try {
                numChars = mIs.read(buf);
            } catch (IOException e) {
                throw new InputMismatchException();
            }
            if (numChars <= 0) {
                return -1;
            }
        }
        return buf[curChar++];
    }
 
    public String nextLine() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(c);
            c = read();
        } while (!isEndOfLine(c));
        return res.toString();
    }
 
    public String next() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(c);
            c = read();
        } while (!isSpaceChar(c));
        return res.toString();
    }
 
    double nextDouble()
    {
        return Double.parseDouble(next());
    }
 
    public long nextLong() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        long res = 0;
        do {
            if (c < '0' || c > '9') {
                throw new InputMismatchException();
            }
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    }
 
    public int nextInt() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        int res = 0;
        do {
            if (c < '0' || c > '9') {
                throw new InputMismatchException();
            }
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    }
 
    public boolean isSpaceChar(int c) {
        return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
    }
 
    public boolean isEndOfLine(int c) {
        return c == '\n' || c == '\r' || c == -1;
    }
 
    } Reader private InputStream mIs; mIs private byte[] buf = new byte[1024]; buf new byte[1024] 1024 private int curChar; curChar private int numChars; numChars public Reader() {
        this(System.in);
    } Reader {
        this(System.in);
    } this(System.in) this System.in System System.in public Reader(InputStream is) {
        mIs = is;
    } Reader {
        mIs = is;
    } mIs = is mIs is InputStream is is public int read() {
        if (numChars == -1) {
            throw new InputMismatchException();
 
    }
        if (curChar >= numChars) {
            curChar = 0;
            try {
                numChars = mIs.read(buf);
            } catch (IOException e) {
                throw new InputMismatchException();
            }
            if (numChars <= 0) {
                return -1;
            }
        }
        return buf[curChar++];
    } read {
        if (numChars == -1) {
            throw new InputMismatchException();
 
    }
        if (curChar >= numChars) {
            curChar = 0;
            try {
                numChars = mIs.read(buf);
            } catch (IOException e) {
                throw new InputMismatchException();
            }
            if (numChars <= 0) {
                return -1;
            }
        }
        return buf[curChar++];
    } if (numChars == -1) {
            throw new InputMismatchException();
 
    } numChars == -1 numChars -1 1 {
            throw new InputMismatchException();
 
    } throw new InputMismatchException(); new InputMismatchException() if (curChar >= numChars) {
            curChar = 0;
            try {
                numChars = mIs.read(buf);
            } catch (IOException e) {
                throw new InputMismatchException();
            }
            if (numChars <= 0) {
                return -1;
            }
        } curChar >= numChars curChar numChars {
            curChar = 0;
            try {
                numChars = mIs.read(buf);
            } catch (IOException e) {
                throw new InputMismatchException();
            }
            if (numChars <= 0) {
                return -1;
            }
        } curChar = 0 curChar 0 try {
                numChars = mIs.read(buf);
            } catch (IOException e) {
                throw new InputMismatchException();
            } catch (IOException e) {
                throw new InputMismatchException();
            } IOException e {
                throw new InputMismatchException();
            } throw new InputMismatchException(); new InputMismatchException() {
                numChars = mIs.read(buf);
            } numChars = mIs.read(buf) numChars mIs.read(buf) mIs.read mIs buf if (numChars <= 0) {
                return -1;
            } numChars <= 0 numChars 0 {
                return -1;
            } return -1; -1 1 return buf[curChar++]; buf[curChar++] buf curChar++ curChar public String nextLine() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(c);
            c = read();
        } while (!isEndOfLine(c));
        return res.toString();
    } nextLine {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(c);
            c = read();
        } while (!isEndOfLine(c));
        return res.toString();
    } int c = read(); c read() read while (isSpaceChar(c)) {
            c = read();
        } isSpaceChar(c) isSpaceChar c {
            c = read();
        } c = read() c read() read StringBuilder res = new StringBuilder(); res new StringBuilder() do {
            res.appendCodePoint(c);
            c = read();
        } while (!isEndOfLine(c)); !isEndOfLine(c) isEndOfLine(c) isEndOfLine c {
            res.appendCodePoint(c);
            c = read();
        } res.appendCodePoint(c) res.appendCodePoint res c c = read() c read() read return res.toString(); res.toString() res.toString res public String next() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(c);
            c = read();
        } while (!isSpaceChar(c));
        return res.toString();
    } next {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(c);
            c = read();
        } while (!isSpaceChar(c));
        return res.toString();
    } int c = read(); c read() read while (isSpaceChar(c)) {
            c = read();
        } isSpaceChar(c) isSpaceChar c {
            c = read();
        } c = read() c read() read StringBuilder res = new StringBuilder(); res new StringBuilder() do {
            res.appendCodePoint(c);
            c = read();
        } while (!isSpaceChar(c)); !isSpaceChar(c) isSpaceChar(c) isSpaceChar c {
            res.appendCodePoint(c);
            c = read();
        } res.appendCodePoint(c) res.appendCodePoint res c c = read() c read() read return res.toString(); res.toString() res.toString res double nextDouble()
    {
        return Double.parseDouble(next());
    } nextDouble {
        return Double.parseDouble(next());
    } return Double.parseDouble(next()); Double.parseDouble(next()) Double.parseDouble Double next() next public long nextLong() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        long res = 0;
        do {
            if (c < '0' || c > '9') {
                throw new InputMismatchException();
            }
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    } nextLong {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        long res = 0;
        do {
            if (c < '0' || c > '9') {
                throw new InputMismatchException();
            }
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    } int c = read(); c read() read while (isSpaceChar(c)) {
            c = read();
        } isSpaceChar(c) isSpaceChar c {
            c = read();
        } c = read() c read() read int sgn = 1; sgn 1 if (c == '-') {
            sgn = -1;
            c = read();
        } c == '-' c '-' {
            sgn = -1;
            c = read();
        } sgn = -1 sgn -1 1 c = read() c read() read long res = 0; res 0 do {
            if (c < '0' || c > '9') {
                throw new InputMismatchException();
            }
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c)); !isSpaceChar(c) isSpaceChar(c) isSpaceChar c {
            if (c < '0' || c > '9') {
                throw new InputMismatchException();
            }
            res *= 10;
            res += c - '0';
            c = read();
        } if (c < '0' || c > '9') {
                throw new InputMismatchException();
            } c < '0' || c > '9' c < '0' c '0' c > '9' c '9' {
                throw new InputMismatchException();
            } throw new InputMismatchException(); new InputMismatchException() res *= 10 res 10 res += c - '0' res c - '0' c '0' c = read() c read() read return res * sgn; res * sgn res sgn public int nextInt() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        int res = 0;
        do {
            if (c < '0' || c > '9') {
                throw new InputMismatchException();
            }
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    } nextInt {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        int res = 0;
        do {
            if (c < '0' || c > '9') {
                throw new InputMismatchException();
            }
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    } int c = read(); c read() read while (isSpaceChar(c)) {
            c = read();
        } isSpaceChar(c) isSpaceChar c {
            c = read();
        } c = read() c read() read int sgn = 1; sgn 1 if (c == '-') {
            sgn = -1;
            c = read();
        } c == '-' c '-' {
            sgn = -1;
            c = read();
        } sgn = -1 sgn -1 1 c = read() c read() read int res = 0; res 0 do {
            if (c < '0' || c > '9') {
                throw new InputMismatchException();
            }
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c)); !isSpaceChar(c) isSpaceChar(c) isSpaceChar c {
            if (c < '0' || c > '9') {
                throw new InputMismatchException();
            }
            res *= 10;
            res += c - '0';
            c = read();
        } if (c < '0' || c > '9') {
                throw new InputMismatchException();
            } c < '0' || c > '9' c < '0' c '0' c > '9' c '9' {
                throw new InputMismatchException();
            } throw new InputMismatchException(); new InputMismatchException() res *= 10 res 10 res += c - '0' res c - '0' c '0' c = read() c read() read return res * sgn; res * sgn res sgn public boolean isSpaceChar(int c) {
        return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
    } isSpaceChar {
        return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
    } return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1; c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1 c == '\t' c == '\r' c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1 c == ' ' c ' ' c == '\n' c '\n' c == '\r' c '\r' c == '\t' c '\t' c == -1 c -1 1 int c c public boolean isEndOfLine(int c) {
        return c == '\n' || c == '\r' || c == -1;
    } isEndOfLine {
        return c == '\n' || c == '\r' || c == -1;
    } return c == '\n' || c == '\r' || c == -1; c == '\n' || c == '\r' || c == -1 c == '\n' || c == '\r' || c == -1 c == '\n' c '\n' c == '\r' c '\r' c == -1 c -1 1 int c c public class Main {
    static PrintWriter out = new PrintWriter(System.out);
    static Reader in = new Reader();
    public static void main(String[] args) throws IOException {
        Main solver = new Main();
        solver.solve();
        out.flush();
        out.close();
 
    }
 
    static int INF = (int)1e9;
    static int maxn = (int)2e4+5;
    static int mod  = 1000*1000*1000+7;
    static int n,m,q,k,t;
    
    void solve() throws IOException{
        long len = in.nextLong();
        
        long[] p = new long[15];
        p[0] = 1;
        for (int i = 1; i < 15; i++) p[i] = p[i-1]*26L;
        
        StringBuilder ans = new StringBuilder("");
        long cur = 1, cnt = 1;
        while (len != 0) {
            cnt*=26L;
            
            if (cnt < len) { 
                len -= cnt;
                cur++;
            } else {
                for (int i = 0; i < cur; i++) {
                    for (int j = 0; j < 26; j++) {
                        if (len-p[(int)cur-i-1] > 0) {
                            len -= p[(int)cur-i-1];
                            continue;
                        } else {
                            ans.append((char)(j+'a')+"");
                            break;
                        }
                    }
                }
                len = 0;
            }
        }
        out.println(ans);
    }
    
    //<>
    
    
    static class Reader {
 
    private InputStream mIs;
    private byte[] buf = new byte[1024];
    private int curChar;
    private int numChars;
 
    public Reader() {
        this(System.in);
    }
 
    public Reader(InputStream is) {
        mIs = is;
    }
 
    public int read() {
        if (numChars == -1) {
            throw new InputMismatchException();
 
    }
        if (curChar >= numChars) {
            curChar = 0;
            try {
                numChars = mIs.read(buf);
            } catch (IOException e) {
                throw new InputMismatchException();
            }
            if (numChars <= 0) {
                return -1;
            }
        }
        return buf[curChar++];
    }
 
    public String nextLine() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(c);
            c = read();
        } while (!isEndOfLine(c));
        return res.toString();
    }
 
    public String next() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(c);
            c = read();
        } while (!isSpaceChar(c));
        return res.toString();
    }
 
    double nextDouble()
    {
        return Double.parseDouble(next());
    }
 
    public long nextLong() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        long res = 0;
        do {
            if (c < '0' || c > '9') {
                throw new InputMismatchException();
            }
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    }
 
    public int nextInt() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        int res = 0;
        do {
            if (c < '0' || c > '9') {
                throw new InputMismatchException();
            }
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    }
 
    public boolean isSpaceChar(int c) {
        return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
    }
 
    public boolean isEndOfLine(int c) {
        return c == '\n' || c == '\r' || c == -1;
    }
 
    }
} public class Main {
    static PrintWriter out = new PrintWriter(System.out);
    static Reader in = new Reader();
    public static void main(String[] args) throws IOException {
        Main solver = new Main();
        solver.solve();
        out.flush();
        out.close();
 
    }
 
    static int INF = (int)1e9;
    static int maxn = (int)2e4+5;
    static int mod  = 1000*1000*1000+7;
    static int n,m,q,k,t;
    
    void solve() throws IOException{
        long len = in.nextLong();
        
        long[] p = new long[15];
        p[0] = 1;
        for (int i = 1; i < 15; i++) p[i] = p[i-1]*26L;
        
        StringBuilder ans = new StringBuilder("");
        long cur = 1, cnt = 1;
        while (len != 0) {
            cnt*=26L;
            
            if (cnt < len) { 
                len -= cnt;
                cur++;
            } else {
                for (int i = 0; i < cur; i++) {
                    for (int j = 0; j < 26; j++) {
                        if (len-p[(int)cur-i-1] > 0) {
                            len -= p[(int)cur-i-1];
                            continue;
                        } else {
                            ans.append((char)(j+'a')+"");
                            break;
                        }
                    }
                }
                len = 0;
            }
        }
        out.println(ans);
    }
    
    //<>
    
    
    static class Reader {
 
    private InputStream mIs;
    private byte[] buf = new byte[1024];
    private int curChar;
    private int numChars;
 
    public Reader() {
        this(System.in);
    }
 
    public Reader(InputStream is) {
        mIs = is;
    }
 
    public int read() {
        if (numChars == -1) {
            throw new InputMismatchException();
 
    }
        if (curChar >= numChars) {
            curChar = 0;
            try {
                numChars = mIs.read(buf);
            } catch (IOException e) {
                throw new InputMismatchException();
            }
            if (numChars <= 0) {
                return -1;
            }
        }
        return buf[curChar++];
    }
 
    public String nextLine() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(c);
            c = read();
        } while (!isEndOfLine(c));
        return res.toString();
    }
 
    public String next() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(c);
            c = read();
        } while (!isSpaceChar(c));
        return res.toString();
    }
 
    double nextDouble()
    {
        return Double.parseDouble(next());
    }
 
    public long nextLong() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        long res = 0;
        do {
            if (c < '0' || c > '9') {
                throw new InputMismatchException();
            }
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    }
 
    public int nextInt() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        int res = 0;
        do {
            if (c < '0' || c > '9') {
                throw new InputMismatchException();
            }
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    }
 
    public boolean isSpaceChar(int c) {
        return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
    }
 
    public boolean isEndOfLine(int c) {
        return c == '\n' || c == '\r' || c == -1;
    }
 
    }
} Main
import java.util.*;
import java.io.*;
import java.math.*;
 
public class Main {
    static PrintWriter out = new PrintWriter(System.out);
    static Reader in = new Reader();
    public static void main(String[] args) throws IOException {
        Main solver = new Main();
        solver.solve();
        out.flush();
        out.close();
 
    }
 
    static int INF = (int)1e9;
    static int maxn = (int)2e4+5;
    static int mod  = 1000*1000*1000+7;
    static int n,m,q,k,t;
    
    void solve() throws IOException{
        long len = in.nextLong();
        
        long[] p = new long[15];
        p[0] = 1;
        for (int i = 1; i < 15; i++) p[i] = p[i-1]*26L;
        
        StringBuilder ans = new StringBuilder("");
        long cur = 1, cnt = 1;
        while (len != 0) {
            cnt*=26L;
            
            if (cnt < len) { 
                len -= cnt;
                cur++;
            } else {
                for (int i = 0; i < cur; i++) {
                    for (int j = 0; j < 26; j++) {
                        if (len-p[(int)cur-i-1] > 0) {
                            len -= p[(int)cur-i-1];
                            continue;
                        } else {
                            ans.append((char)(j+'a')+"");
                            break;
                        }
                    }
                }
                len = 0;
            }
        }
        out.println(ans);
    }
    
    //<>
    
    
    static class Reader {
 
    private InputStream mIs;
    private byte[] buf = new byte[1024];
    private int curChar;
    private int numChars;
 
    public Reader() {
        this(System.in);
    }
 
    public Reader(InputStream is) {
        mIs = is;
    }
 
    public int read() {
        if (numChars == -1) {
            throw new InputMismatchException();
 
    }
        if (curChar >= numChars) {
            curChar = 0;
            try {
                numChars = mIs.read(buf);
            } catch (IOException e) {
                throw new InputMismatchException();
            }
            if (numChars <= 0) {
                return -1;
            }
        }
        return buf[curChar++];
    }
 
    public String nextLine() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(c);
            c = read();
        } while (!isEndOfLine(c));
        return res.toString();
    }
 
    public String next() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(c);
            c = read();
        } while (!isSpaceChar(c));
        return res.toString();
    }
 
    double nextDouble()
    {
        return Double.parseDouble(next());
    }
 
    public long nextLong() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        long res = 0;
        do {
            if (c < '0' || c > '9') {
                throw new InputMismatchException();
            }
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    }
 
    public int nextInt() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        int res = 0;
        do {
            if (c < '0' || c > '9') {
                throw new InputMismatchException();
            }
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    }
 
    public boolean isSpaceChar(int c) {
        return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
    }
 
    public boolean isEndOfLine(int c) {
        return c == '\n' || c == '\r' || c == -1;
    }
 
    }
}