// #define DEBUGGING
#include <bits/stdc++.h>
#define endl '\n'
#define ALL(V) (V).begin(), (V).end()
#define ALLR(V) (V).rbegin(), (V).rend()
using ll = std::int64_t;
using ull = std::uint64_t;
using PLL = std::pair<ll, ll>;
using TLL = std::tuple<ll, ll, ll>;
template <typename T> using V = std::vector<T>;
template <typename T> using VV = V<V<T>>;
template <typename T> const T& var_min(const T &t) { return t; }
template <typename T> const T& var_max(const T &t) { return t; }
template <typename T, typename... Tail> const T& var_min(const T &t, const Tail&... tail) { return std::min(t, var_min(tail...)); }
template <typename T, typename... Tail> const T& var_max(const T &t, const Tail&... tail) { return std::max(t, var_max(tail...)); }
template <typename T, typename... Tail> void chmin(T &t, const Tail&... tail) { t = var_min(t, tail...); }
template <typename T, typename... Tail> void chmax(T &t, const Tail&... tail) { t = var_max(t, tail...); }
template <typename T> const T& clamp(const T &t, const T &low, const T &high) { return std::max(low, std::min(high, t)); }
template <typename T> void chclamp(T &t, const T &low, const T &high) { return t = clamp(t, low, high); }
namespace init__ { struct InitIO { InitIO() { std::cin.tie(nullptr); std::ios_base::sync_with_stdio(false); std::cout << std::fixed << std::setprecision(30); } } init_io; }
#define mv_rec make_v(init, tail...)
template <typename T> T make_v(T init) { return init; }
template <typename T, typename... Tail> auto make_v(T init, size_t s, Tail... tail) { return V<decltype(mv_rec)>(s, mv_rec); }
#undef mv_rec
using namespace std;

#ifdef DEBUGGING
#include "../../debug/debug.cpp"
#else
#define DEBUG(...) 0
#define DEBUG_SEPARATOR_LINE 0
#endif


const size_t SIZE = 5010;

struct Bit {
    int *data;
    int id_ele = 0;

    Bit() : Bit(nullptr) { }

    Bit(int *data) : data(data) { }

    int sum(int pos) {
        int ret = id_ele;
        for(--pos; 0 < pos; pos -= pos & -pos) ret += data[pos];
        return ret;
    }

    int sum(int l, int r) { 
        return sum(r + 1) - sum(l); 
    }

    void add(int pos, int delta) {
        for(; pos < SIZE; pos += pos & -pos) data[pos] += delta;
    }
};

int bit_arr[2][SIZE][SIZE];
Bit bit_l[SIZE], bit_r[SIZE];
int cnt_l[SIZE], cnt_r[SIZE];
int A[SIZE];
int N, X;

int main() {
    cin >> N >> X;
    for (int i = 0; i < N; i++) cin >> A[i];

    auto make_cnt = [&](int cnt_v[]) {
        int l = 0, r = 0;
        int sum = 0;
        for (int l = 0; l < N; l++) {
            while (r < N && sum + A[r] <= X) {
                sum += A[r];
                r++;
            }
            cnt_v[l] = r - l;
            sum -= A[l];
        }
    };

    make_cnt(cnt_l);
    reverse(A, A + N);
    make_cnt(cnt_r);
    reverse(A, A + N);
    reverse(cnt_r, cnt_r + N);
    for (int i = N; 1 <= i; i--) {
        cnt_l[i] = cnt_l[i - 1];
        cnt_r[i] = cnt_r[i - 1];
    }

    for (int i = 1; i <= N; i++) {
        bit_l[i] = Bit(bit_arr[0][i]);
        bit_r[i] = Bit(bit_arr[1][i]);
    }

    for (int i = 1; i <= N; i++) bit_r[i].add(i, 1);
    
    int suma[SIZE];
    for (int i = 0; i < N; i++) suma[i + 1] = suma[i] + A[i];

    for (int len = 2; len <= N; len++) {
        for (int l = 1; l <= N; l++) {
            int r = l + len;
            if (N < r) break;
            
            {
                int rv = min(r, l + cnt_l[l]);
                int cnt = bit_r[r].sum(l + 1, rv);
                if (cnt) bit_l[l].add(r, 1);
            }
            
            {
                int lv = max(l, r - cnt_r[r]);
                int cnt = bit_l[l].sum(lv, r - 1);
                if (cnt == (r - 1) - lv + 1) bit_r[r - 1].add(l, 1);
            }
        }
    }
    
    cout << (bit_l[1].sum(N, N) == 1 ? "A" : "B") << endl;
    return 0;
}