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

namespace ConsoleApplication3
{
	class Program
	{
		private static readonly List<char> ConvertTable = Enumerable.Range(0x41, 26).Select(x => (char) x).ToList();
		static void Main(string[] args)
		{
			var n = long.Parse(Console.ReadLine());
			var buff = new List<char> {ConvertTable[(int) (n%26)]};
			while ((n /= 26) != 0)
			{
				buff.Add(ConvertTable[(int) (--n%26)]);
			}
			buff.Reverse();
			Console.WriteLine(buff.Aggregate(new StringBuilder(), (b, c) => b.Append(c)).ToString());
		}
	}
}