#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import string


def generate_sequence(n):
    def gen(result, x):
        if x < 0:
            return result
        else:
            d, m = divmod(x, 26)
            char = string.ascii_uppercase[m]
            return gen(char + result, d - 1)
    return gen("", n)


main = lambda: print(generate_sequence(int(input())))


if __name__ == '__main__':
    main()