using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ForYukicoder
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = long.Parse(Console.ReadLine());
            string ans = "";
            while (n != -1)
            {
                ans = Convert.ToChar('A' + n % 26) + ans;
                n = n / 26 - 1;
            }

            Console.WriteLine(ans);
        }
    }
}