#define _USE_MATH_DEFINES
#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define MT make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define RT return
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;

const int MA = 5003;
int lr[MA][MA], rl[MA][MA], toLeft[MA], toRight[MA];

void solve() {
    int N, X;
    cin >> N >> X;
    vi A(N);
    rep(i, N) {
        cin >> A[i];
    }
    rep(i, N) {
        ll sum = 0;
        FOR(j, i, N) {
            sum += A[j];
            if (sum > X) {
                break;
            }
            // [i, j]
            toRight[i] = j + 1;
        }
        sum = 0;
        for (int j = i; j >= 0; --j) {
            sum += A[j];
            if (sum > X) {
                break;
            }
            // [j, i]
            toLeft[i] = j;
        }
    }

    int res = 0;
    for (int len = 2; len <= N; ++len) {
        for (int i = 0; i + len <= N; ++i) {
            lr[i][i + len] += lr[i][i + len - 1];
            rl[i + len][i] += rl[i + len][i + 1];
            res = lr[i][i + len] + rl[i + len][i] > 0 ? 1 : 0;
            if (res == 0) {
                lr[i][i + len + 1]++;
                lr[i][toRight[i + len] + 1]--;
                if (i > 0) {
                    rl[i + len][i - 1]++;
                    if (toLeft[i] > 0) {
                        rl[i + len][toLeft[i] - 1]--;
                    }
                }
            }
        }
    }

    cout << (res ? 'A' : 'B') << endl;
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout << fixed << setprecision(15);
	solve();
	return 0;
}