#include <bits/stdc++.h>
using namespace std;

template<typename T>
struct BIT {
    int n;
    vector<T> dat;

    BIT(int n=0){
        initialize(n);
    }

    void initialize(int nin){
        n = nin;
        dat.resize(n, 0);
    }

    T sum(int i){
        T s = 0;
        while(i >= 0){
            s += dat[i];
            i = (i & (i+1)) - 1;
        }
        return s;
    }

    T sum_between(int i, int j){
        return sum(j) - sum(i-1);
    }

    void plus(int i, T x){
        while(i < n){
            dat[i] += x;
            i |= i+1;
        }
    }

    // a[0]+...+a[ret] >= x
    int lower_bound(T x){
        if(x < 0) return -1;
        int ret = -1;
        int k = 1;
        while(2*k <= n) k <<= 1;
        for( ;k>0; k>>=1){
            if(ret+k < n && dat[ret+k] < x){
                x -= dat[ret+k];
                ret += k;
            }
        }
        return ret + 1;
    }
};

int main(){
    int N, X;
    cin >> N >> X;
    vector<int64_t> A(N), S(N+1);
    for(int i=0; i<N; i++){
        cin >> A[i];
        S[i+1] = S[i] + A[i];
    }
    vector<int> lnxt(N), rnxt(N);
    int ng = 0;
    for(int l=0; l<N; l++){
        while(ng <= N && S[ng]-S[l] <= X) ng++;
        lnxt[l] = ng-1;
    }
    ng = N-1;
    for(int r=N-1; r>=0; r--){
        while(ng >= 0 && S[r]-S[ng] <= X) ng--;
        rnxt[r] = ng;
    }

    BIT<int> bit_L2R[5000], bit_R2L[5000];
    for(int i=0; i<N; i++){
        bit_L2R[i].initialize(N);
        bit_R2L[i].initialize(N);
        bit_L2R[i].plus(i, 1);
        bit_R2L[i].plus(i, 1);
    }
    for(int d=1; d<N; d++) for(int l=0; l+d<N; l++){
        int r = l+d;
        int lose = 1;
        if(bit_R2L[r].sum_between(l+1, min(lnxt[l], r))) lose = 0;
        if(bit_L2R[l].sum_between(max(l, rnxt[r]), r-1)) lose = 0;
        if(lose){
            bit_L2R[l].plus(r, 1);
            bit_R2L[r].plus(l, 1);
        }
    }
    int first_lose = bit_L2R[0].sum_between(N-1, N-1);
    cout << (first_lose ? "B" : "A") << endl;
    return 0;
}