#B:キャンディーボックス3
N = int(input())
C = list(map(int,input().split(" ")))

C.reverse()

count2 = 0
count1 = 0
for i in C:
	if i >= 3:
		print("B")
		exit(0)
	elif i == 2:
		count2 += 1
		if count2 == 2:
			print("B")
			exit(0)
	elif i == 1:
		count1 += 1

if (count1 + 2)%2 == 1:
	print("A")
else:
	print("B")