#include <cstdio>
#include <iostream>
#include <string>
#include <sstream>
#include <stack>
#include <algorithm>
#include <cmath>
#include <queue>
#include <map>
#include <set>
#include <cstdlib>
#include <bitset>
#include <tuple>
#include <assert.h>
#include <deque>
#include <bitset>
#include <iomanip>
#include <limits>
#include <chrono>
#include <random>
#include <array>
#include <unordered_map>
#include <functional>
#include <complex>

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

const long long MAX = 5100000;
const long long INF = 1LL << 60;
const long long mod = 1000000007LL;
//const long long mod = 998244353LL;

using namespace std;
typedef unsigned long long ull;
typedef long long ll;

class BIT {
private:
	ll N;
	vector<ll> node;
public:
	BIT(ll M) {
		node = vector<ll>(M + 1, 0);
		N = M;
	}

	ll sum(ll i) {
		ll s = 0;
		while (i > 0) {
			s += node[i];
			i -= i & -i;
		}
		return s;
	}

	ll sum(ll i, ll j) {
		ll l = sum(i - 1);
		ll r = sum(j);
		return r - l;
	}

	void add(ll i, ll x) {
		while (i <= N) {
			node[i] += x;
			i += i & -i;
		}
	}
};


int main()
{
	/*
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	*/

	ll N, X; scanf("%lld %lld", &N, &X);
	vector<ll> a(N); for (ll i = 0; i < N; i++) scanf("%lld", &a[i]);
	vector<ll> rb(N);
	vector<ll> lb(N);
	for (ll i = 0; i < N; i++) {
		ll j = i;
		ll sum = 0;
		while (j < N && sum + a[j] <= X) {
			rb[i] = j;
			sum += a[j];
			j++;
		}
	}
	for (ll i = N - 1; i >= 0; i--) {
		ll j = i;
		ll sum = 0;
		while (j >= 0 && sum + a[j] <= X) {
			lb[i] = j;
			sum += a[j];
			j--;
		}
	}

	vector<BIT> vbl(N, BIT(N + 1)), vbr(N, BIT(N + 1));

	for (ll len = 1; len <= N; len++) {
		for (ll left = 0; left + len - 1 < N; left++) {
			ll right = left + len - 1;
			ll lose = 1;
			//cout << right << endl;
			if (vbl[left].sum(max(left, lb[right] - 1) + 1, right)) lose = 0;
			if (vbr[right].sum(left + 2, min(right, rb[left] + 1) + 1)) lose = 0;
			if (lose) {
				vbl[left].add(right + 1, 1);
				vbr[right].add(left + 1, 1);
			}
			//cout << left << " " << right << " " << rb[left]<<" "<<lb[right]<< " "<<vbl[left].sum(right + 1, right + 1) << " " << vbr[right].sum(left + 1, left + 1) << endl;
		}
	}
	if (vbl[0].sum(N,N)) puts("B");
	else puts("A");
	return 0;
}