import sys, numpy as np
n, x = map(int, input().split())
a = np.genfromtxt(sys.stdin, dtype=int)
b = np.vstack((np.zeros((2, n), dtype=int), a, a))
while b.shape[1] > 1:
	b, c = b[:,:-1], b[:,1:]
	b[0] += c[2]
	b[1] = c[1] + b[3]
	b[2] = c[2]
	b[:2, np.logical_and(b[0]>x, b[1]>x)] = 0
print("A" if b[0,0] else "B")