import numpy as np

n, x = tuple(map(int, input().split()))
a = list(map(int, input().split()))


left = np.zeros(n, dtype=np.int32)
right = np.zeros(n, dtype=np.int32)
l = 0
r = 0
s = 0

while True:
    while r != n and  s + a[r] <= x:
        s += a[r]
        r += 1
    left[l] = r - l
    s -= a[l]
    l += 1
    if l == n:
        break

l = n - 1
r = n - 1
s = 0

while True:
    while l != -1 and s + a[l] <= x:
        s += a[l]
        l -= 1
    right[r] = r - l
    s -= a[r]
    r -= 1
    if r < 0:
        break

dp_l = np.zeros((n, n + 1), dtype=np.int32)
dp_r = np.zeros((n, n + 1), dtype=np.int32)


i = 0
j = 0
while i <= n:
    while j < n:
        if i == 0:
            dp_l[j,i] = 0
            dp_r[j,i] = 0
            j += 1
            continue
        l = j
        r = j + i - 1
        if r >= n:
            break
        cnt = min(left[l], i - 1)
        x = dp_r[r,i - 1] - dp_r[r,i - cnt - 1]
        if x != cnt:
            dp_l[l,i] = dp_l[l,i - 1] + 1
            dp_r[r,i] = dp_r[r,i - 1] + 1
            j += 1
            continue

        cnt = min(right[r], i - 1)
        x = dp_l[l,i - 1] - dp_l[l,i - cnt - 1]
        if x != cnt:
            dp_l[l,i] = dp_l[l,i - 1] + 1
            dp_r[r,i] = dp_r[r,i - 1] + 1
            j += 1
            continue
        dp_l[l,i] = dp_l[l,i - 1]
        dp_r[r,i] = dp_r[r,i - 1]
        j += 1
    i += 1
    j = 0

if dp_l[0,n] == dp_l[0,n - 1]:
    print("B")
else:
    print("A")