# coding: utf-8
# Your code here!
import sys
sys.setrecursionlimit(10**6)
readline = sys.stdin.readline
read = sys.stdin.read

n,x,*a = [int(i) for i in read().split()]

r = [0]*n #r[i]= iから左にどこまで伸ばせるか
l = [0]*n #l[i]= iから右に...
pt = res = 0
for i in range(n-1):
    res -= a[i] 
    while pt < n and res+a[pt] <= x:
        res += a[pt]
        pt += 1
    r[i] = pt

pt,res = n-1, 0
for i in range(n-1,0,-1):
    res -= a[i]
    while pt >= 0 and res+a[pt] <= x:
        res += a[pt]
        pt -= 1
    l[i] = pt+1

dp = [[0]*n for _ in range(n)]
for i in range(n-1,-1,-1):
    j = i
    while j < n:
        if dp[i][j]:
            j += 1
        else: #0の場合、そこは負けで、上、右に1をのばす
            dp[i][j] = -1
            for k in range(l[i],i):
                dp[k][j] = 1
            dp[i][j+1:r[j]] = [1]*(r[j]-(j+1))
            j = r[j]

if dp[0][-1] == 1:
    print("A")
else:
    print("B")