#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; }
//---------------------------------------------------------------------------------------------------
template<class V, int NV> struct BIT {
    BIT() {}  // [L, R)
    V bit[NV << 1];
    V operator[](int e) { V s = 0; e++; while (e) s += bit[e - 1], e -= e&-e; return s; }
    void add(int e, V v) { e++; while (e <= NV) bit[e - 1] += v, e += e&-e; }
    int lower_bound(V val) { 
        V tv = 0; int i, ent = 0; for (i = NV - 1; i >= 0; i--)
        if(tv+bit[ent+(1<<i)-1]<=val)tv+=bit[ent+(1<<i)-1],ent += (1 << i);return ent;
    }
    V get(int L, int R) {
        assert(0 <= L); assert(R <= NV); assert(L <= R);
        V res = 0; if(R) res += operator[](R - 1); if (L) res -= operator[](L - 1);return res;
    }
    void clear() { rep(i, 0, NV) bit[i] = 0; }
	void update(int e, V v) { add(e, v - get(e, e + 1)); }
};
/*---------------------------------------------------------------------------------------------------
　　　　　　　　　　　 ∧＿∧
　　　　　 ∧＿∧ 　（´<_｀ ）　 Welcome to My Coding Space!
　　　　 （ ´_ゝ`）　/　 ⌒i     @hamayanhamayan0
　　　　／　　　＼　 　  |　|
　　　 /　　 /￣￣￣￣/　　|
　 ＿_(__ﾆつ/　    ＿/ .| .|＿＿＿＿
　 　　　＼/＿＿＿＿/　（u　⊃
---------------------------------------------------------------------------------------------------*/














int N, X, A[5010];
BIT<int, 1<<12> lft[5010], rht[5010];
//---------------------------------------------------------------------------------------------------
ll B[5010];
// [l,r]
ll get(int l, int r) {
	ll res = B[r];
	if (l) res -= B[l - 1];
	return res;
}
//---------------------------------------------------------------------------------------------------
void _main() {
	cin >> N >> X;
	rep(i, 0, N) cin >> A[i];

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

	rep(len, 1, N + 1) {
		rep(l, 0, N - len + 1) {
			int r = l + len - 1;
			lft[l].update(r, 1);
			rht[r].update(l, 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++;

			if (rht[r].get(l + 1, ng) != 0) {
				lft[l].update(r, 0);
				rht[r].update(l, 0);
			}
		}

		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--;

			if (lft[l].get(ng + 1, r) != 0) {
				lft[l].update(r, 0);
				rht[r].update(l, 0);
			}
		}
	}

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