# coding: utf-8
# Here your code !

def convert(N):
    X = 26**8
    res = ""
    while X:
        if N >= X:
            res += chr(ord('A') + N/X - 1)
            N -= N/X*X
        X /= 26
    return res

N = int(raw_input())
print convert(N + 1)