#include <bits/stdc++.h>
using namespace std;

int main() {
  ios::sync_with_stdio(false);

  int N, X;
  cin >> N >> X;

  vector<int> A(N);
  for (int i = 0; i < N; ++i) cin >> A[i];

  vector<int64_t> pa(N + 1);
  for (int i = 0; i < N; ++i) pa[i + 1] = pa[i] + A[i];

  vector<vector<int>> pdp(N, vector<int>(N + 1));
  vector<vector<int>> sdp(N, vector<int>(N + 1));
  for (int i = 0; i < N; ++i) pdp[i][0] = 1;
  for (int i = 0; i < N; ++i) sdp[i][0] = 1;
  for (int len = 1; len <= N; ++len) {
    for (int i = 0; i + len <= N; ++i) {
      int win = 0; {
        int lb = 1;
        int ub = len + 1;
        while (ub - lb > 1) {
          int mb = lb + ub >> 1;
          (pa[i + mb] - pa[i] <= X ? lb : ub) = mb;
        }
        win |= sdp[i + len - 1][len - 1] - (len - lb - 1 < 0 ? 0 : sdp[i + len - 1][len - lb - 1]) < lb;
      } {
        int lb = 1;
        int ub = len + 1;
        while (ub - lb > 1) {
          int mb = lb + ub >> 1;
          (pa[i + len] - pa[i + len - mb] <= X ? lb : ub) = mb;
        }
        win |= pdp[i][len - 1] - (len - lb - 1 < 0 ? 0 : pdp[i][len - lb - 1]) < lb;
      }
      pdp[i][len] = pdp[i][len - 1] + win;
      sdp[i + len - 1][len] = sdp[i + len - 1][len - 1] + win;
    }
  }

  int fwin = pdp[0][N] - pdp[0][N - 1];
  assert(fwin == sdp[N - 1][N] - sdp[N - 1][N - 1]);
  cout << "AB"[fwin ^ 1] << endl;

  return 0;
}