#include <bits/stdc++.h>
using namespace std;
#define modulo 1000000007
#define mod(mod_x) ((((long long)mod_x+modulo))%modulo)
#define Inf 10000000000000000



int main(){
	
	int N,X;
	cin>>N>>X;
	
	vector<int> a(N);
	for(int i=0;i<N;i++){
		cin>>a[i];
	}
	
	vector<int> left(N),right(N);
	
	int l = 0;
	int r = 0;
	int sum = 0;
	
	while(true){
		while(r != N && sum + a[r] <= X){
			sum += a[r];
			r++;
		}
		left[l] = r-l;
		sum -= a[l];
		l++;
		if(l==N)break;
	}
	
	l=N-1;
	r=N-1;
	sum=0;
	
	while(true){
		while(l!=-1&&sum+a[l]<=X){
			sum += a[l];
			l--;
		}
		right[r] = r-l;
		sum -= a[r];
		r--;
		if(r<0)break;
	}
	
	
	//vector<vector<int>> dp_l(N,vector<int>(N+1)),dp_r(N,vector<int>(N+1));
	int dp_l[5000][5001],dp_r[5000][5001];
	
	for(int i=0;i<N;i++){
		dp_l[i][0]=0;
		dp_r[i][0]=0;
	}
	
	for(int i=1;i<=N;i++){
		for(int j=0;j<N;j++){
			int l = j;
			int r = j+i-1;
			if(r>=N)break;
			
			dp_l[l][i]=dp_l[l][i-1];
			dp_r[r][i]=dp_r[r][i-1];
			
			int cnt = min(left[l],i-1);
			int x = dp_r[r][i-1]-dp_r[r][i-cnt-1];
			if(x!=cnt){
				dp_l[l][i]++;
				dp_r[r][i]++;
				continue;
			}
			
			cnt = min(right[r],i-1);
			x = dp_l[l][i-1]-dp_l[l][i-cnt-1];
			if(x!=cnt){
				dp_l[l][i]++;
				dp_r[r][i]++;
				continue;
			}
			
		}
	}

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


	return 0;
}