#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n, x; cin >> n >> x;
	vector<int>a(n);
	rep(i, n)cin >> a[i];
	vector<int>left(n), right(n);
	rep(_, 2) {
		long long sum = 0;
		int j = 0;
		for (int i = 0; i < n; ++i) {
			while (j < n && sum + a[j] <= x) {
				sum += a[j];
				j++;
			}
			left[i] = j - i;
			sum -= a[i];
		}
		reverse(all(a));
		swap(left, right);
	}
	reverse(all(right));
	// 手番の状態、勝ちなら1負けなら0を累積和で持つ
	vector dpl(n, vector<int>(n + 2, 0));
	vector dpr(n, vector<int>(n + 2, 0));
	rep2(i, 1, n + 1) {
		rep(j, n) {
			// 閉区間
			int l = j;
			int r = l + i - 1;
			if (r >= n)break;
			dpl[l][i + 0] = dpl[l][i - 1];
			dpr[r][i + 0] = dpr[r][i - 1];
			{
				int can = min(i - 1, left[l]);
				int x = dpr[r][i - 1] - dpr[r][i - can - 1];
				if (x != can) {
					dpl[l][i + 0]++;
					dpr[r][i + 0]++;
					continue;
				}
			}
			int can = min(i - 1, right[r]);
			int x = dpl[l][i - 1] - dpl[l][i - can - 1];
			if (x != can) {
				dpl[l][i + 0]++;
				dpr[r][i + 0]++;
			}
		}
	}
	if (dpl[0][n + 0] == dpl[0][n - 1])cout << "B" << endl;
	else cout << "A" << endl;
	return 0;
}