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 (true)
            {
                ans = Convert.ToChar(n % 26 + 'A') + ans;
                n = n / 26 - 1;
                if(n == -1)
                {
                    break;
                }
            }
        
            Console.WriteLine(ans);

        }
    }
}