N = int(input())
C = list(map(int, input().split()))

zero = 0
one = 0

for i in range(N):
    if C[i] == 0:
        zero += 1
    elif C[i] == 1:
        one += 1
    elif C[i] == 2:
        continue
    else:
        print('B')
        break
else:
    if zero + one == N:
        if one % 2 == 0:
            print('B')
        else:
            print('A')
    elif zero + one == N - 1:
        if one % 2 == 0:
            print('B')
        else:
            print('A')
    else:
        print('B')