#include<bits/stdc++.h>
#define rep(i,a,b) for(int i=a;i<b;i++)
#define rrep(i,a,b) for(int i=a;i>=b;i--)
#define fore(i,a) for(auto &i:a)
#define all(x) (x).begin(),(x).end()
//#pragma GCC optimize ("-O3")
using namespace std; void _main(); int main() { cin.tie(0); ios::sync_with_stdio(false); _main(); }
typedef long long ll; const int inf = INT_MAX / 2; const ll infl = 1LL << 60;
template<class T>bool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; }
//---------------------------------------------------------------------------------------------------
/*---------------------------------------------------------------------------------------------------
　　　　　　　　　　　 ∧＿∧
　　　　　 ∧＿∧ 　（´<_｀ ）　 Welcome to My Coding Space!
　　　　 （ ´_ゝ`）　/　 ⌒i     @hamayanhamayan0
　　　　／　　　＼　 　  |　|
　　　 /　　 /￣￣￣￣/　　|
　 ＿_(__ﾆつ/　    ＿/ .| .|＿＿＿＿
　 　　　＼/＿＿＿＿/　（u　⊃
---------------------------------------------------------------------------------------------------*/














int N, X, A[5010];
int lft[5010][5010], rht[5010][5010];
//---------------------------------------------------------------------------------------------------
ll B[5010];
// [l,r]
ll get(int l, int r) {
	ll res = B[r];
	if (l) res -= B[l - 1];
	return res;
}
//---------------------------------------------------------------------------------------------------
int ng_lft[5010], ng_rht[5010];
void make_ng() {
	rep(len, 2, N + 1) {
		int ng = 0;
		rep(l, 0, N - len + 1) {
			int r = l + len - 1;
			while (ng <= l) ng++;
			while (ng <= r and get(l, ng) <= X) ng++;
			ng_lft[l] = ng;
		}

		ng = N;
		rrep(r, N - len, len - 1) {
			int l = r - len + 1;
			while (r <= ng) ng--;
			while (l <= ng and get(ng, r) <= X) ng--;
			ng_rht[r] = ng;
		}
	}
}
//---------------------------------------------------------------------------------------------------
void _main() {
	cin >> N >> X;
	rep(i, 0, N) cin >> A[i];

	if (N == 1) {
		cout << "B" << endl;
		return;
	}

	B[0] = A[0];
	rep(i, 1, N) B[i] = B[i - 1] + A[i];

	make_ng();

	rep(i, 0, N) {
		lft[i][i] = 1;
		rht[i][i] = 1;
	}

	rep(len, 2, N + 1) {
		int ng = 0;
		rep(l, 0, N - len + 1) {
			int r = l + len - 1;

			rht[r][l] = rht[r][l + 1];
			lft[l][r] = lft[l][r - 1];

			int tot = rht[r][ng_lft[l] - 1] - rht[r][l];
			int cnt = ng_lft[l] - 1 - (l + 1) + 1;
			if (tot != cnt) {
				rht[r][l]++;
				lft[l][r]++;
				continue;
			}

			tot = lft[l][r] - lft[l][ng_rht[r]];
			cnt = r - (ng_rht[r] + 1) + 1;
			if (tot != cnt) {
				rht[r][l]++;
				lft[l][r]++;
				continue;
			}
		}
	}

	if (lft[0][N - 1] == lft[0][N - 2] + 1) cout << "A" << endl;
	else cout << "B" << endl;
}