N = int(input())
if N == 1:
    print("B")
elif N <= 8:
    print("A")
elif N <= 24:
    if N % 2 == 1:
        print("B")
    else:
        print("A")
elif N <= 96:
    print("A")
else:
    if N % 2 == 1:
        print("B")
    else:
        print("A")