#include<bits/stdc++.h>

using namespace std;

typedef long long ll;

ll N,X;

vector<ll> a;

int dp[5010][5010][2];

//閉じた区間[l,r]について考える

bool rec(ll l, ll r, bool turn){
  
  int c = 0;
  if(turn){ c = 1;}
  
  if( dp[l][r][c] != -1){ return dp[l][r][c];}
  
  if( r-l == 0){ //１つのみが残っている時　このターンに回ってきた方が負ける
    return !turn;
  }
  else{
   ll left = l; ll right = r;
    
    ll res1 = 0,res2 = 0;
   
    if( turn ){ // Aのターンの時
  
     while(left < r && res1+a[left] <= X){ 
       res1 += a[left];
       left++;
       
      if( rec(left,r,!turn) == true ){ dp[l][r][1] = 1; return true;}
       //一つでもtrueが返せる瞬間があったら、Aは勝てる
       
    }
      
      while(right > l && res2+a[right] <= X){
        res2 += a[right];
        right--;
      if( rec(l,right,!turn) == true ){ dp[l][r][1] = 1; return true;}
        
      }
      
      dp[l][r][1] = 0;
      
      return false;
      
    }
    
    else{
      
      while(left < r && res1+a[left] <= X){
        res1 += a[left];
        left++;
        if( rec(left,r,!turn) == false ){ dp[l][r][0] = 0;return false;}
        
      }
      
      while(right > l && res2+a[right] <= X){
        res2 += a[right];
        right--;
        if( rec(l,right,!turn) == false){ dp[l][r][0] = 0; return false;}
        
      }
      
      dp[l][r][0] = 1;
      return true;
    }
    
  }
}
 
int main(){ 
  
  cin >> N >> X; a.resize(N);
  
  for(ll i = 0; i < N; i++){ cin >> a[i];}
  
  for(int i = 0; i < 5010; i++){
    for(int j = 0; j < 5010; j++){
      dp[i][j][0] = -1; dp[i][j][1] = -1;
    }
  }
 
  bool res = rec(0,N-1,true);
  
  if( res ){ cout << "A" << endl;}
  else{ cout <<"B" << endl;}
  
  return 0;
}