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 fst = new[] {ConvertTable[(int) (n%26)]};

			var sec =
				Enumerable.Range(0, 10000).Select(_ =>
				{
					n /= 26;
					return n;
				}).TakeWhile(x => x != 0).Select(x => ConvertTable[(int) (--n%26)]);


			var foo = fst.Concat(sec).Reverse().ToArray();




			Console.WriteLine(foo.Aggregate(new StringBuilder(), (b, c) => b.Append(c)).ToString());
		}
	}
}