using System;
using System.Collections.Generic;
using System.Linq;

namespace yukicoder
{
    public class Program
    {
        public static void Main()
        {
            var n = long.Parse(Console.ReadLine()) + 1;
            var a = new List<long>();
            while (n > 26)
            {
                a.Add(n % 26); 
                n /= 26;
            }
            a.Add(n);
            var A = a.Select(x => (char)(x + 'A' - 1));
            foreach(var b in A)
            {
                Console.Write(b);
            }
            Console.WriteLine();
        }
    }
}