using System;

namespace No327{
    public class Program{
        public static void Main(string[] args){
            var N = long.Parse(Console.ReadLine());

            var res = "";
            while(N >= 0){
                res = (char)(N % 26 + 'A') + res;
                N = N / 26 - 1;
            }

            Console.WriteLine(res);
        }
    }
}