import std.stdio, std.array, std.string, std.conv, std.algorithm;
import std.typecons, std.range, std.random, std.math, std.container;
import std.numeric, std.bigint, core.bitop, core.stdc.stdio;

void main() {
    auto s = readln.split.map!(to!int);
    auto N = s[0];
    auto X = s[1].to!long;
    auto A = readln.split.map!(to!long).array;

    auto B = new long[](N+1);
    foreach (i; 0..N) B[i+1] = B[i] + A[i];

    long sum(int l, int r) {
        if (r < l) return 0;
        return B[r+1] - B[l];
    }

    int calc_left(int l, int r) {
        int hi = r + 1;
        int lo = l;
        while (hi - lo > 1) {
            int mid = (hi + lo) / 2;
            if (sum(l, mid) <= X) lo = mid;
            else hi = mid;
        }
        return lo;
    }

    int calc_right(int l, int r) {
        int hi = r;
        int lo = l - 1;
        while (hi - lo > 1) {
            int mid = (hi + lo) / 2;
            if (sum(mid, r) <= X) hi = mid;
            else lo = mid;
        }
        return hi;
    }

    auto ans = new bool[][](N, N);
    auto minr = new int[](N);
    auto maxl = new int[](N);
    foreach (i; 0..N) minr[i] = maxl[i] = i;

    foreach (len; 2..N+1) foreach (l; 0..N-len+1) {
        int r = l + len - 1;
        int nr = calc_right(l, r) - 1;
        int nl = calc_left(l, r) + 1;
        if (nr <= minr[l] || nl >= maxl[r]) {
            ans[l][r] = true;
        } else {
            minr[l] = r;
            maxl[r] = l;
        }
    }

    writeln(ans[0][N-1] ? "A" : "B");
}