using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using static System.Console;
using static System.Math;
using static System.Array;

class Program
{
    public static void Main()
    {
        var n = long.Parse(ReadLine());
        string s = "";
        while(n > 0)
        {
            s = (char)(n % 26 + 'a' - 1) + s;
            n /= 26;
        }
        WriteLine(s);
    }
}
