n, x = map(int, input().split())
a = list(map(int, input().split()))
n = len(a)
pre_sum = [0] * (n + 1)
for i in range(1, n + 1):
    pre_sum[i] = pre_sum[i - 1] + a[i - 1]

# 预处理k_max
k_max = [0] * (n + 2)
for l in range(1, n + 1):
    low = 1
    high = n - l + 1
    best = 0
    while low <= high:
        mid = (low + high) // 2
        end = l + mid - 1
        if end > n:
            high = mid - 1
            continue
        s = pre_sum[end] - pre_sum[l - 1]
        if s <= x:
            best = mid
            low = mid + 1
        else:
            high = mid - 1
    k_max[l] = best

# 预处理m_max
m_max = [0] * (n + 2)
for r in range(1, n + 1):
    low = 1
    high = r
    best = 0
    while low <= high:
        mid = (low + high) // 2
        start = r - mid + 1
        if start < 1:
            high = mid - 1
            continue
        s = pre_sum[r] - pre_sum[start - 1]
        if s <= x:
            best = mid
            low = mid + 1
        else:
            high = mid - 1
    m_max[r] = best

# 初始化dp
dp = [[False] * (n + 2) for _ in range(n + 2)]

# 填充dp表
for length in range(0, n):
    for l in range(1, n - length + 1):
        r = l + length
        if l > r:
            dp[l][r] = False
            continue
        possible = False
        # 检查左边吃k个的情况
        max_k = k_max[l]
        for k in range(1, max_k + 1):
            new_l = l + k
            if new_l > r:
                continue
            if not dp[new_l][r]:
                possible = True
                break
        if possible:
            dp[l][r] = True
            continue
        # 检查右边吃m个的情况
        max_m = m_max[r]
        for m in range(1, max_m + 1):
            new_r = r - m
            if new_r < l:
                continue
            if not dp[l][new_r]:
                possible = True
                break
        dp[l][r] = possible

if dp[1][n]:
    print("A")
else:
    print("B")