#include <bits/stdc++.h>

using namespace std;

using int64 = long long;
const int mod = 1e9 + 7;
//const int mod = 998244353;

const int64 infll = (1LL << 62) - 1;
const int inf = (1 << 30) - 1;

struct IoSetup {
  IoSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    cerr << fixed << setprecision(10);
  }
} iosetup;


template< typename T1, typename T2 >
ostream &operator<<(ostream &os, const pair< T1, T2 > &p) {
  os << p.first << " " << p.second;
  return os;
}

template< typename T1, typename T2 >
istream &operator>>(istream &is, pair< T1, T2 > &p) {
  is >> p.first >> p.second;
  return is;
}

template< typename T >
ostream &operator<<(ostream &os, const vector< T > &v) {
  for(int i = 0; i < (int) v.size(); i++) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}

template< typename T >
istream &operator>>(istream &is, vector< T > &v) {
  for(T &in : v) is >> in;
  return is;
}

template< typename T1, typename T2 >
inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }

template< typename T1, typename T2 >
inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }

template< typename T = int64 >
vector< T > make_v(size_t a) {
  return vector< T >(a);
}

template< typename T, typename... Ts >
auto make_v(size_t a, Ts... ts) {
  return vector< decltype(make_v< T >(ts...)) >(a, make_v< T >(ts...));
}

template< typename T, typename V >
typename enable_if< is_class< T >::value == 0 >::type fill_v(T &t, const V &v) {
  t = v;
}

template< typename T, typename V >
typename enable_if< is_class< T >::value != 0 >::type fill_v(T &t, const V &v) {
  for(auto &e : t) fill_v(e, v);
}

template< typename F >
struct FixPoint : F {
  FixPoint(F &&f) : F(forward< F >(f)) {}

  template< typename... Args >
  decltype(auto) operator()(Args &&... args) const {
    return F::operator()(*this, forward< Args >(args)...);
  }
};

template< typename F >
inline decltype(auto) MFP(F &&f) {
  return FixPoint< F >{forward< F >(f)};
}

int main() {
  int N, X;
  cin >> N >> X;
  vector< int > A(N);
  cin >> A;

  vector< int > AR(N);
  int64 ptr = 0, sum = 0;
  for(int i = 0; i < N; i++) {
    while(ptr < N && sum + A[ptr] <= X) {
      sum += A[ptr];
      ++ptr;
    }
    AR[i] = ptr - 1;
    sum -= A[i];
  }
  vector< int > AL(N);
  ptr = N - 1, sum = 0;
  for(int i = N - 1; i >= 0; i--) {
    while(ptr >= 0 && sum + A[ptr] <= X) {
      sum += A[ptr];
      --ptr;
    }
    AL[i] = ptr + 1;
    sum -= A[i];
  }

  bitset< 5000 > dp[5000], dp2[5000];
  for(int i = 0; i < N; i++) {
    for(int j = 0; j < N; j++) {
      dp[i][j] = dp2[i][j] = true;
    }
  }

  bitset< 5000 > sufmask[5000];
  for(int i = 0; i < 5000; i++) {
    for(int j = i; j < N; j++) sufmask[i][j] = true;
  }
  bitset< 5000 > premask[5000];
  for(int i = 0; i < 5000; i++) {
    for(int j = 0; j <= i; j++) premask[i][j] = true;
  }


  for(int len = 2; len <= N; len++) {
    for(int left = 0; left <= N - len; left++) {
      int right = left + len - 1;

      //leftより手前のやつ
      if((dp2[right] & premask[min(N - 1, AR[left] + 1)]).count()) {
        dp[left][right] = false;
        dp2[right][left] = false;
      } else if((dp[left] & sufmask[max(0, AL[right] - 1)]).count()) {
        dp[left][right] = false;
        dp2[right][left] = false;
      }


    }
  }
  if(dp[0][N - 1]) cout << "B" << endl;
  else cout << "A" << endl;
}