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

#define int long long
#define rep(i,l,r) for(int i=(int)(l);i<(int)(r);i++)
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)x.size())
template<class T>bool chmax(T &a,T b){if(a<b){a=b;return 1;}return 0;}
template<class T>bool chmin(T &a,T b){if(a>b){a=b;return 1;}return 0;}

/*
 */

using vi = vector<int>;
using vvi = vector<vi>;
using P = pair<int,int>;

signed main() {
  int n, x;
  cin >> n >> x;

  vi a(n);
  rep(i, 0, n) cin >> a[i];

  vi lr(n), rl(n);
  {
    int r = 0, sum = 0;
    rep(l, 0, n){
      while(r < n and sum + a[r] <= x){
        sum += a[r];
        r++;
      }

      lr[l] = r-1;

      if(l == r) r++;
      else sum -= a[l];
    }
  }

  {
    int l = n-1, sum = 0;
    for(int r = n-1; r >= 0; r--){
      while(l >= 0 and sum + a[l] <= x){
        sum += a[l];
        l--;
      }

      rl[r] = l+1;

      if(l == r) l--;
      else sum -= a[r];
    }
  }

  vvi dp(n+1, vi(n, 1)); // dp[len][left]

  rep(len, 2, n+1){
    vi sdp(n+1);
    rep(i, 0, n) sdp[i+1] = sdp[i] + dp[len-1][i];

    rep(left, 0, n){
      if(left+len-1 >= n) break;

      int l = left, r = left+len-1;
      int s = lr[l], t = rl[r];
      if(sdp[s+1]-sdp[l] > 0){
        dp[len][left] = 0;
      }
      if(sdp[r+1]-sdp[t] > 0){
        dp[len][left] = 0;
      }
    }
  }

//  rep(len, 0, n+1) {
//    rep(left, 0, n) {
//      cout << dp[len][left] << " ";
//    }
//    cout << endl;
//  }

  if(dp[n][0]) cout << "B" << endl;
  else cout << "A" << endl;

  return 0;
}