import string


def radix_convert(number, radix):
    s = []
    while number > 0:
        s.append(number % radix)
        number = number // radix
    return s[::-1]


N = int(input())
if N == 0:
    print('A')
    exit()
else:
    S = ''.join(string.ascii_uppercase[e - 1] for e in radix_convert(N, 26))
    T = string.ascii_uppercase[N % 26]
    print(S[:-1] + T)