using System;

class Alphabet
{

	static  public void Main(string[] args)
	{
		long N = long.Parse(Console.ReadLine());
		string alphabet = "";
		string ABC = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

		while(true)
		{
			int i = (int)(N % 26);
			alphabet = ABC.Substring(i, 1) + alphabet;
			if(N / 26 == 0)
				break;
			N = N / 26 - 1;
		}
		Console.WriteLine(alphabet);
	}

}