#pragma comment (linker, "/STACK:256000000")
#define  _CRT_SECURE_NO_WARNINGS
#include "bits/stdc++.h"

using namespace std;
typedef string::const_iterator State;
#define eps 1e-11L
#define MAX_MOD 1000000007LL
#define GYAKU 500000004LL

#define MOD 998244353LL
#define seg_size 262144
#define pb push_back
#define mp make_pair
typedef long long ll;
#define REP(a,b) for(long long (a) = 0;(a) < (b);++(a))
#define ALL(x) (x).begin(),(x).end()
void init() {
	iostream::sync_with_stdio(false);
	cout << fixed << setprecision(100);
}
bool ans[5000][5000] = {};
bool visited[5000][5000] = {};
int next_go[2][5000 * 5000] = {};
int union_find(int now, bool dir) {
	if (next_go[dir][now] == now) return now;
	return next_go[dir][now] = union_find(next_go[dir][now], dir);
}
pair<int, int> to_pair(int now) {
	return mp(now / 5000, now % 5000);
}
int to_int(pair<int,int> now) {
	return now.first * 5000 + now.second;
}
ll summing[7000] = {};
ll calc_sum(int a, int b) {
	return summing[b+1] - summing[a];
}
void solve() {
	ll n, x;
	cin >> n >> x;
	vector<ll> inputs;
	REP(i, n) {
		int a;
		cin >> a;
		inputs.pb(a);
	}
	for (int i = 0; i < inputs.size(); ++i) {
		summing[i + 1] += inputs[i] + summing[i];
	}
	for (int i = inputs.size(); i + 1 < 7000; ++i) {
		summing[i + 1] = summing[i];
	}
	REP(i, 5000) {
		REP(q, 5000) {
			next_go[0][i*5000+q] = next_go[1][i*5000+q] = i*5000+q;
		}
	}
	for (int i = 0; i < n; ++i) {
		for (int q = i; q >= 0; --q) {
			if (ans[i][q] == 1) continue;
			{
				//dir = 0
				while (true) {
					int next = union_find(i * 5000 + q, 0);
					if (next/5000 == 0) break;
					if (calc_sum(next/5000 - 1, i - 1) > x) break;
					ans[next/5000 - 1][q] = 1;
					next_go[0][next] = next - 5000;
				}
			}
			{
				//dir = 1
				while (true) {
					int next = union_find(i * 5000 + q, 1);
					if (next % 5000 == n-1) break;
					if (calc_sum(q+1, next % 5000 + 1) > x) break;
					ans[next / 5000][next % 5000 + 1] = 1;
					next_go[1][next] = next + 1;
				}
			}
		}
	}
	if (ans[0][n - 1] == 0) {
		cout << "B" << endl;
	}
	else {
		cout << "A" << endl;
	}
	return;
}

#undef int

int main() {
	init();
	solve();
}