N = int(input())
alphabets = [chr(i) for i in range(ord('A'), ord('A') + 26)]


def encode_x_base(n, x):
    if n == 0:
        return [0]

    ret = []
    while n:
        ret.append(n % x)
        n //= x

    return ret[::-1]


encoded_N_26_based = encode_x_base(N, 26)
ans = [alphabets[i - 1] for i in encoded_N_26_based[:-1]] + [alphabets[encoded_N_26_based[-1]]]
print(''.join(ans))