#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;
}

vector<bitset<5001>> dp(5001);

set<int> st_l[5001],st_r[5001];

void solve(){
    int n;ll x;cin>>n>>x;
    vector<ll> v(n);
    cin>>v;

    vector<ll> s(n);
    s[0]=v[0];
    for(int i=1;i<n;i++) s[i]=s[i-1]+v[i];
    rep(i,n) st_l[i].insert(i+1);
    rep(i,n) st_r[i+1].insert(i);

    for(int w=2;w<=n;w++){
        for(int l=0;l+w<=n;l++){
            int r=l+w;// [l,r)
            bool win=false;
            // left
            {
                ll offset=(l==0?0:s[l-1]);
                int ri=lower_bound(begin(s),end(s),offset+x+1)-begin(s);
                // can take [l,r)
                auto ite=st_r[r].lower_bound(l+1);
                if(ite!=end(st_r[r]) and *ite<=ri) win=true;
            }
            // right
            {
                int li=lower_bound(begin(s),end(s),s[r-1]-x+1)-begin(s);
                // can take [li,r)
                auto ite=st_l[l].lower_bound(li);
                if(ite!=end(st_l[l]) and *ite<r) win=true;
            }
            dp[l][r]=win;
            if(!win){
                st_l[l].insert(r);
                st_r[r].insert(l);
            }
        }
    }
    cout<<(dp[0][n]?"A":"B")<<endl;
}

void naive(){
    int n;ll x;cin>>n>>x;
    vector<ll> v(n);
    cin>>v;



    for(int w=2;w<=n;w++){
        for(int l=0;l+w<=n;l++){
            int r=l+w;// [l,r)
            bool win=false;
            // left
            {
                ll s=v[l];
                for(int i=l+1;i<r and s<=x;i++){
                    if(!dp[i][r]) win=true;
                    s+=v[i];
                }
            }
            // right
            {
                ll s=v[r-1];
                for(int i=r-1;i>l and s<=x;i--){
                    if(!dp[l][i]) win=true;
                    s+=v[i-1];
                }
            }
            dp[l][r]=win;
        }
    }
    cout<<(dp[0][n]?"A":"B")<<endl;
}

signed main(){
    // naive();
    solve();
    return 0;
}