#include<bits/stdc++.h>
using namespace std;
#define ALL(x) begin(x),end(x)
#define rep(i,n) for(int i=0;i<(n);i++)
#define debug(v) cout<<#v<<":";for(auto x:v){cout<<x<<' ';}cout<<endl;
#define mod 998244353
using ll=long long;
const int INF=1000000000;
const ll LINF=1001002003004005006ll;
int dx[]={1,0,-1,0},dy[]={0,1,0,-1};
template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return true;}return false;}
template<class T>bool chmin(T &a,const T &b){if(b<a){a=b;return true;}return false;}

struct IOSetup{
    IOSetup(){
        cin.tie(0);
        ios::sync_with_stdio(0);
        cout<<fixed<<setprecision(12);
    }
} iosetup;
 
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==(int)v.size()?"":" ");
    return os;
}
template<typename T>
istream &operator>>(istream &is,vector<T>&v){
    for(T &x:v)is>>x;
    return is;
}



signed main(){
    int n;ll x;cin>>n>>x;
    vector<ll> v(n);
    cin>>v;
    vector<int> t_l(n),t_r(n);// can take [i, t_l[i]], [t_r[i], i]
    
    vector<ll> s(n);
    s[0]=v[0];
    for(int i=1;i<n;i++) s[i]=s[i-1]+v[i];

    for(int i=0;i<n;i++){
        {
            ll offset=(i?s[i-1]:0);
            int r=lower_bound(ALL(s),offset+x+1)-begin(s);
            t_l[i]=r-1;
        }
        {   
            int l=0,r=i,res=i;
            while(l<r){
                int m=(l+r)/2;
                int sum=s[i]-(m?s[m-1]:0);
                if(sum<=x) r=m-1,res=m;
                else       l=m+1;
            }
            t_l[i]=res;
        }
    }


    vector<vector<int>> L(n+2,vector<int>(n+2,0)),R(n+2,vector<int>(n+2,0));
    rep(i,n) L[i][i]=1,R[i][i]=1;

    auto getL=[&](int R,int l,int r){
        int ret=L[l][R];
        if(r+1<=n) ret-=L[r+1][R];
        return ret;
    };
    auto getR=[&](int L,int l,int r){
        int ret=R[L][r];
        if(l) ret-=R[L][l-1];
        return ret;
    };

    bool res=false;
    for(int w=2;w<=n;w++){
        for(int l=0;l+w<=n;l++){
            int r=l+w-1;

            bool win=false;
            int a=t_l[l];// can eat [l,a]
            int b=t_r[r];// [b,r]

            if(getL(r,l+1,a+1)) win=true;
            if(getR(l,b-1,r-1)) win-true;

            L[l][r]=L[l+1][r];
            R[l][r]=R[l][r-1];
            if(!win){
                L[l][r]++;
                R[l][r]++;
            }
            if(l==0 and r==n-1) res=win;
        }
    }
    cout<<("BA"[res])<<endl;
    return 0;
}