//
// Created by yamunaku on 2020/01/17.
//

#include <bits/stdc++.h>

using namespace std;

#define rep(i, n) for(int i = 0; i < (n); i++)
#define repl(i, l, r) for(int i = (l); i < (r); i++)
#define per(i, n) for(int i = ((n)-1); i >= 0; i--)
#define perl(i, l, r) for(int i = ((r)-1); i >= (l); i--)
#define all(x) (x).begin(),(x).end()
#define MOD9 998244353
#define MOD1 1000000007
#define IINF 1000000000
#define LINF 1000000000000000000
#define SP <<" "<<
#define CYES cout<<"Yes"<<endl
#define CNO cout<<"No"<<endl
#define CFS cin.tie(0);ios::sync_with_stdio(false)
#define CST(x) cout<<fixed<<setprecision(x)

using ll = long long;
using ld = long double;
using vi = vector<int>;
using mti = vector<vector<int>>;
using vl = vector<ll>;
using mtl = vector<vector<ll>>;
using pi = pair<int, int>;
using pl = pair<ll, ll>;
template<typename T>
using heap = priority_queue<T, vector<T>, function<bool(const T, const T)>>;

int main(){
    // CFS;
    int n;
    cin >> n;
    ll x;
    cin >> x;
    vl a(n);
    rep(i, n) cin >> a[i];
    vi li(n + 1, 0), lj(n + 1, 0);
    li[n] = n, lj[n] = n;
    ll r = 0;
    int idx = 0;
    rep(i, n){
        while(idx < n){
            if(r + a[idx] > x) break;
            r += a[idx];
            idx++;
        }
        li[i] = idx;
        r -= a[i];
    }
    r = 0;
    idx = 0;
    per(i, n){
        while(idx < n){
            if(r + a[n - 1 - idx] > x) break;
            r += a[n - 1 - idx];
            idx++;
        }
        lj[n - 1 - i] = idx;
        r -= a[i];
    }
    vector<bitset<5001>> dp(5001, bitset<5001>());
    vi ci(n + 1, 0), cj(n + 1, 0);
    rep(i, n + 1){
        rep(j, n + 1){
            if(i + j >= n) dp[i][j] = true;
        }
    }
    per(i, n){
        per(j, n){
            if(i + j >= n) continue;
            repl(k, li[i] + 1, li[i + 1] + 1){
                if(!dp[k][j]) ci[j]--;
            }
            repl(k, lj[j] + 1, lj[j + 1] + 1){
                if(!dp[i][k]) cj[i]--;
            }
            if(ci[j] + cj[i] > 0) dp[i][j] = true;
            if(!dp[i][j]){
                ci[j]++;
                cj[i]++;
            }
        }
    }
//    rep(i, n + 1){
//        rep(j, n + 1){
//            if(dp[i][j]) cout << "1";
//            else cout << "0";
//        }
//        cout << endl;
//    }
    if(dp[0][0]) cout << "A" << endl;
    else cout << "B" << endl;
    return 0;
}