n = input()
a = map(int,raw_input().split())
if n != len(a):exit()
for i in xrange(len(a)):
	if a[i] < 0 or 1000000000 < a[i]:exit()
	if 3 <= a[i]: a[i] = -1
if a.count(-1)==0 and a.count(1)%2==1 and a.count(2)<=1:
	print("A")
else:
	print("B")