import sys

def main():
    n, x = map(int, sys.stdin.readline().split())
    a = list(map(int, sys.stdin.readline().split()))
    pre_sum = [0] * (n + 1)
    for i in range(1, n+1):
        pre_sum[i] = pre_sum[i-1] + a[i-1]
    
    dp = [[False]*(n+2) for _ in range(n+2)]
    
    for length in range(1, n+1):
        for l in range(1, n - length +2):
            r = l + length -1
            found = False
            
            # 处理左边的情况
            max_possible_k = r - l +1
            low = 1
            high = max_possible_k
            best_k = 0
            while low <= high:
                mid = (low + high) // 2
                end = l + mid -1
                if end > r:
                    high = mid -1
                    continue
                s = pre_sum[end] - pre_sum[l-1]
                if s <= x:
                    best_k = mid
                    low = mid +1
                else:
                    high = mid -1
            
            for k in range(1, best_k +1):
                new_l = l + k
                if new_l > r:
                    continue
                if not dp[new_l][r]:
                    found = True
                    break
            
            if found:
                dp[l][r] = True
                continue
            
            # 处理右边的情况
            max_possible_m = r - l +1
            low = 1
            high = max_possible_m
            best_m = 0
            while low <= high:
                mid = (low + high) // 2
                start = r - mid +1
                if start < l:
                    high = mid -1
                    continue
                s = pre_sum[r] - pre_sum[start -1]
                if s <= x:
                    best_m = mid
                    low = mid +1
                else:
                    high = mid -1
            
            for m in range(1, best_m +1):
                new_r = r - m
                if new_r < l:
                    continue
                if not dp[l][new_r]:
                    found = True
                    break
            
            dp[l][r] = found
    
    if dp[1][n]:
        print("A")
    else:
        print("B")

if __name__ == "__main__":
    main()