#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<int> dp(N + 1);
  vector<int> dps(N + 2);
  dp[N] = 1;
  dps[N] = 1;
  repr(i, N) {
    // S[j] > X + S[i]
    int j = upper_bound(range(S), X + S[i]) - S.begin();
    if (dps[i + 1] - dps[j] != j - (i + 1)) {
      dp[i] = 1;
    }
    dps[i] = dps[i + 1] + dp[i];
  }
  cout << (dp[0] ? "A" : "B") << endl;
}