#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, n) for (int i = 0; i < (n); i++)
#define repr(i, n) for (int i = (n) - 1; i >= 0; i--)
#define range(a) a.begin(), a.end()

int main() {
  int N; cin >> N;
  ll X; cin >> X;
  vector<ll> A(N); rep(i, N) cin >> A[i];
  vector<ll> S(N + 1); rep(i, N) S[i + 1] = S[i] + A[i];
  vector<vector<int>> dp(N, vector<int>(N));
  vector<vector<int>> eplr(N, vector<int>(N));
  vector<vector<int>> eprl(N, vector<int>(N));
  for (int d = 1; d <= N - 1; d++) {
    for (int l = 0; l + d <= N - 1; l++) {
      int r = l + d;
      // dpl[l][r]...dpl[x][r] -> 0
      // dpr[l][y]...dpr[l][r] -> 0
      int x, y;
      {
        int lo = l + 1;
        int hi = r + 1;
        while (hi - lo > 1) {
          int mid = (lo + hi) / 2;
          if (S[mid] - S[l] <= X) {
            lo = mid;
          } else {
            hi = mid;
          }
        }
        x = lo;
      }
      {
        int lo = l - 1;
        int hi = r - 1;
        while (hi - lo > 1) {
          int mid = (lo + hi) / 2;
          if (S[r + 1] - S[mid + 1] <= X) {
            hi = mid;
          } else {
            lo = mid;
          }
        }
        y = hi;
      }
      if (eprl[r][l + 1] - eprl[r][x] + dp[x][r] != x - (l + 1) + 1) {
        dp[l][r] = 1;
      }
      if (eplr[l][r - 1] - eplr[l][y] + dp[l][y] != (r - 1) - y + 1) {
        dp[l][r] = 1;
      }
      eplr[l][r] = dp[l][r] + eplr[l][r - 1];
      eprl[r][l] = dp[l][r] + eprl[r][l + 1];
    }
  }
  cout << (dp[0][N - 1] ? "A" : "B") << endl;
}