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)]};


			Console.WriteLine(
				Enumerable.Range(0, 10000)
					.Select(_ => n/26)
					.TakeWhile(x => x != 0)
					.Select(x => ConvertTable[(int) (--n%26)])
					.Reverse()
					.Aggregate(new StringBuilder(), (b, c) => b.Append(c))
					.ToString());

		}
	}
}