using System;
class Program {
    static void Main() {
        long n = 1 + long.Parse(Console.ReadLine());
        string ds = "";
        do {
            long m = n % 26;
            if (m == 0) {
                m += 26;
                n--;
            }
            char c = (char)(m + 64);
            ds = c + ds;
            n /= 26;
        } while (n > 0);

        Console.WriteLine(ds);
    }
}