from functools import lru_cache


@lru_cache(maxsize=None)
def grundy(x):
    if x == 0 or x == 1:
        return 0
    if x == 2:
        return 1
    S = set()
    if x >= 2:
        a = x // 2
        b = x - a
        S.add(grundy(a) ^ grundy(b))
    if x % 3 == 1:
        S.add(grundy(x // 3 + 1))
    else:
        S.add(grundy(x // 3))
    S = sorted(S)
    for i, s in enumerate(S):
        if i == s:
            continue
        return i
    return i + 1


N = int(input())
if grundy(N):
    print("A")
else:
    print("B")