using System;
using System.Globalization;
using System.IO;
using System.Runtime.CompilerServices;
using System.Text;
using static Scanner;

class Solver
{
    static void Main(string[] args) {
        Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false });
        Solve(new Cin<int>(), new Cin<long>(), new Cin<double>(), new Cin<string>());
        Console.Out.Flush();
    }

    static void Solve(Cin<int> ScanInt, Cin<long> ScanLong, Cin<double> ScanDouble, Cin<string> ScanStr) {
        long N = ScanLong;
        var sb = new StringBuilder();
        while (N > 0) {
            var n = N % 26 == 0 ? 26 : N % 26;
            sb.Insert(0, (char) (n + 'a' - 1));
            N = (N - n) / 26;
        }
        Console.WriteLine(sb.ToString());
    }
}

public readonly struct Cin<T>
{
    [MethodImpl(256)]
    public static implicit operator T(in Cin<T> _) => Scan<T>();
    [MethodImpl(256)]
    public T[] Array(int l) {
        var array = new T[l];
        for (int i = 0; i < array.Length; i++) array[i] = Scan<T>();
        return array;
    }
    [MethodImpl(256)]
    public T[,] Array2D(int x, int y) {
        var array = new T[x, y];
        for (int i = 0; i < x; ++i) for (int j = 0; j < x; ++j) array[i, j] = Scan<T>();
        return array;
    }
}

public class Scanner
{
    const int BUFFER_SIZE = 1024, CHAR_BEGIN = 33, CHAR_END = 126, CHAR_ZERO = 48, CHAR_NINE = 57;
    static readonly Stream stdin;
    static readonly byte[] buffer;
    static int size, p;
    static bool isEof;
    static Scanner() {
        stdin = Console.OpenStandardInput();
        buffer = new byte[BUFFER_SIZE];
    }
    [MethodImpl(256)]
    private static byte Read() {
        if (isEof) return default;
        if (p < size) return buffer[p++];
        p = 0;
        if ((size = stdin.Read(buffer, 0, BUFFER_SIZE)) > 0) return buffer[p++];
        isEof = true;
        return 0;
    }
    [MethodImpl(256)]
    private static char Next() {
        byte b;
        do b = Read();
        while (!(CHAR_BEGIN <= b && b <= CHAR_END));
        return (char) b;
    }
    [MethodImpl(256)]
    private static string Str() {
        var sb = new StringBuilder();
        for (var c = Next(); CHAR_BEGIN <= c && c <= CHAR_END; c = (char) Read()) {
            sb.Append(c);
        }
        return sb.ToString();
    }
    [MethodImpl(256)]
    private static int Int() {
        int temp = 0;
        for (var c = Next(); CHAR_ZERO <= c && c <= CHAR_NINE; c = (char) Read()) {
            temp = temp * 10 + c - CHAR_ZERO;
        }
        return temp;
    }
    [MethodImpl(256)]
    private static long Long() {
        long temp = 0;
        for (var c = Next(); CHAR_ZERO <= c && c <= CHAR_NINE; c = (char) Read()) {
            temp = temp * 10 + c - CHAR_ZERO;
        }
        return temp;
    }
    [MethodImpl(256)]
    private static double Double() => double.Parse(Str(), CultureInfo.InvariantCulture);
    [MethodImpl(256)]
    public static string ScanStrLine() {
        var sb = new StringBuilder();
        for (var c = Next(); c != '\n' && c != 0; c = (char) Read()) if (c != '\r') sb.Append(c);
        return sb.ToString();
    }
    [MethodImpl(256)]
    public static T Scan<T>() {
        if (typeof(T) == typeof(int)) {
            var i = Int();
            return Unsafe.As<int, T>(ref i);
        }
        if (typeof(T) == typeof(long)) {
            var l = Long();
            return Unsafe.As<long, T>(ref l);
        }
        if (typeof(T) == typeof(string)) {
            var s = Str();
            return Unsafe.As<string, T>(ref s);
        }
        if (typeof(T) == typeof(double)) {
            var d = Double();
            return Unsafe.As<double, T>(ref d);
        }
        return default;
    }
}

Measured memory_bytes: 23732