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

namespace yukicoder
{
    public class Program
    {
        public static void Main()
        {
            var n = long.Parse(Console.ReadLine());
            long i = 26;
            long j = 1;
            while (n >= i)
            {
                n -= i;
                i *= 26;
                j++;
            }
            var a = new long[j];
            for (i = 0; i < j; i++)
            {
                a[j - 1 - i] = n % 26;
                n /= 26;
            }
            foreach(var m in a)
            {
                Console.Write((char)(m + 'A'));
            }
            Console.WriteLine();
        }
    }
}