using System;

class Program
{
    static void Main()
    {
        long n = long.Parse(Console.ReadLine());

        string ans = "";

        while (n >= 0)
        {
            ans = (char)(n % 26 + 'A') + ans;
            n = n / 26 - 1; ;
        }

        Console.WriteLine(ans);
    }
}