N = int(input())
C = list(map(int,input().split()))
if N == 1:
    if C[0] == 1:
        print('A')
    else:
        print('B')
else:
    x = C.count(1)
    y = C.count(2)
    if x + y == N and y == 1:
        print('A')
    else:
        print('B')