// #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;
using BS = bitset<SIZE>;

set<ll> idx0[SIZE];
set<ll, greater<ll>> idx1[SIZE];
BS dp0[SIZE], dp1[SIZE];
BS mask0[SIZE], mask1[SIZE];
ll A[SIZE];
ll N, X;
ll max_r[SIZE], max_l[SIZE];
const ll inf = 5e15;
bool calc0(ll i, ll j);
bool calc1(ll i, ll j);

void shaku(ll max_v[]) {
    ll l = 0, r = 0;
    ll sum = 0;
    for (ll l = 0; l < N; l++) {
        while (r < N && sum + A[r] <= X) {
            sum += A[r];
            r++;
        }
        max_v[l] = r - l;
        sum -= A[l];
    }
}

bool calc0(ll i, ll j) {
    while (true) {
        ll r = *idx0[i].lower_bound(i + 1);
        if (abs(r) == inf || i + max_r[i] < r) break;
        calc1(r, j);
        idx0[i].erase(r);
    }
    bool win = (dp1[j] & mask0[i]).count() < mask0[i].count();
    dp0[i].set(j, win);
    dp1[j].set(i, !win);
    return win;
}

bool calc1(ll i, ll j) {
    while (true) {
        ll l = *idx1[j].lower_bound(j - 1);
        if (abs(l) == inf || l < j - max_l[j]) break;
        calc0(i, l);
        idx1[j].erase(l);
    }
    bool win = (dp0[i] & mask1[j]).count() < mask1[j].count();
    dp1[j].set(i, win);
    dp0[i].set(j, !win);
    return win;
}

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

    for (ll i = 0; i <= N; i++) {
        for (ll j = i + 1; j <= N; j++) idx0[i].insert(j);
        for (ll j = 0; j < i; j++) idx1[i].insert(j);
        idx0[i].insert(inf);
        idx1[i].insert(inf);
        idx0[i].insert(-inf);
        idx1[i].insert(-inf);
    }

    shaku(max_r);
    reverse(A, A + N);
    shaku(max_l);
    reverse(A, A + N);
    reverse(max_l, max_l + N);

    for (ll i = 0; i < N; i++) {
        ll l = i;
        ll r = i + max_r[i] - 1;
        BS bs;
        for (ll j = l; j < r; j++) bs.set(j, 1);
        mask0[i] = bs;
    }

    for (ll i = 0; i < N; i++) {
        ll r = i;
        ll l = r - (max_l[i] - 1);
        DEBUG(make_tuple(l,r));
        BS bs;
        for (ll j = l; j < r; j++) bs.set(j, 1);
        mask1[i] = bs;
    }

    cout << (calc0(0, N - 1) ? "A" : "B") << endl;
    return 0;
}