n, x = map(int, input().split())
a = list(map(int, input().split())) + [x+1]
f, b = [0] * (n+1), [0] * (n+1)
i, j, s = -1, -1, 0
while i < n:
	if s > x:
		f[i] = j
		i += 1
		s -= a[i]
	else:
		j += 1
		s += a[j]
		b[j] = i
f[n-1] = 0
for j in range(n):
	i = b[j]
	while i >= 0:
		if f[i] <= j:
			f[i] = f[j]
			i = b[i]
		else:
			i -= 1
print("A" if f[0] else "B")