N = int(input())
C = [int(i) for i in input().split()]
count = 0
result = "A"
for i in range(N):
    if C[i] >= 3:
        result = "B"
        break
    if C[i] >= 2:
        count += 1
    if count >= 2:
        result="B"
        break
print(result)