#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)};
}

template< class T >
struct BinaryIndexedTree {
  vector< T > data;

  BinaryIndexedTree(int sz) {
    data.assign(++sz, 0);
  }

  T sum(int k) {
    T ret = 0;
    for(++k; k > 0; k -= k & -k) ret += data[k];
    return (ret);
  }

  void add(int k, T x) {
    for(++k; k < data.size(); k += k & -k) data[k] += x;
  }
};


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];
  }

  vector< BinaryIndexedTree< int > > dp1(N, BinaryIndexedTree< int >(N));
  vector< BinaryIndexedTree< int > > dp2(N, BinaryIndexedTree< int >(N));


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

      bool f = false;

      // dp[left][AL[right] - 1 ... N) に false があるか
      {
        int l = max(0, AL[right] - 1);
        int r = N;
        if(dp1[left].sum(r - 1) - dp1[left].sum(l - 1) < r - l) f = true;
      }

      // dp[0, AR[left] + 1)[right] に false があるか
      {
        int l = 0;
        int r = min(N - 1, AR[left] + 1);
        if(dp2[right].sum(r - 1) - dp2[right].sum(l - 1) < r - l) f = true;
      }

      if(f) {
        dp1[left].add(right, 1);
        dp2[right].add(left, 1);
      }

    }
  }
  if(dp1[0].sum(N - 1) - dp1[0].sum(N - 2)) cout << "A" << endl;
  else cout << "B" << endl;
}