#include <iostream>
#include <algorithm>
#define llint long long
#define inf 1e18

using namespace std;

llint n, x;
llint a[5005], sum[5005];
llint dp[5005][5005], dpsum[5005][5005];

llint get(llint sl, llint sr, llint tl, llint tr)
{
	return dpsum[tl][tr] - dpsum[tl][sr-1] - dpsum[sl+1][tr] + dpsum[sl+1][sr-1];
}

int main(void)
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	
	cin >> n >> x;
	for(int i = 1; i <= n; i++) cin >> a[i];
	for(int i = 1; i <= n; i++) sum[i] = sum[i-1] + a[i];
	
	for(int l = n; l >= 1; l--){
		for(int r = 1; r <= n; r++){
			if(r-l < 0) continue;
			if(r-l == 0) dp[l][r] = 1;
			else{
				llint res = 0;
				llint p = upper_bound(sum, sum+n+1, sum[l-1]+x) - sum;
				if(p > r) res++;
				else res += get(p, r, l+1, r);
				
				//cout << l << " " << r << " " << p << " " << get(l+1, r, p, r) << endl;
				
				p = lower_bound(sum, sum+n+1, sum[r]-x) - sum;
				if(p < l) res++;
				else res += get(l, p, l, r-1);
				
				//cout << l << " " << r << " " << p << endl;
				
				if(res > 0) dp[l][r] = 0;
				else dp[l][r] = 1;
			}
			dpsum[l][r] = dpsum[l+1][r] + dpsum[l][r-1] - dpsum[l+1][r-1] + dp[l][r];
		}
	}
	
	/*for(int i = 1; i <= n; i++){
		for(int j = 1; j <= n; j++){
			cout <<dp[i][j]<< " ";
		}
		cout << endl;
	}*/
	
	if(dp[1][n]) cout << "B" << endl;
	else cout << "A" << endl;
	
	return 0;
}