using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using System.Threading;
using System.Text;
using System.Diagnostics;
using static util;
using P = pair<int, int>;
using Number = System.Int32;

class Program {
    static void Main(string[] args) {
        var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
        var solver = new Solver(sw);
        // var t = new Thread(solver.solve, 1 << 26); // 64 MB
        // t.Start();
        // t.Join();
        solver.solve();
        sw.Flush();
    }
}

class Solver {
    StreamWriter sw;
    Scan sc;
    void Prt(string a) => sw.WriteLine(a);
    void Prt<T>(IEnumerable<T> a) => Prt(string.Join(" ", a));
    void Prt(params object[] a) => Prt(string.Join(" ", a));
    public Solver(StreamWriter sw) {
        this.sw = sw;
        this.sc = new Scan();
    }
    public void solve() {
        int n, x;
        sc.Multi(out n, out x);
        var a = sc.IntArr;
        Prt(solve2(n, x, a) ? 'A' : 'B');
    }

    bool solve1(int n, int x, int[] a) {
        var dp = new bool[n][];
        for (int i = 0; i < n; i++)
        {
            dp[i] = new bool[n + 1];
            dp[i][i] = true;
        }
        for (int d = 2; d <= n; d++)
        {
            for (int l = 0; l + d <= n; l++)
            {
                int r = l + d;
                for (int i = l, sum = 0; i < r; i++)
                {
                    sum += a[i];
                    if (sum > x) break;
                    if (!dp[i + 1][r]) {
                        dp[l][r] = true;
                        break;
                    }
                }
                for (int i = r - 1, sum = 0; i >= l ; i--)
                {
                    sum += a[i];
                    if (sum > x) break;
                    if (!dp[l][i]) {
                        dp[l][r] = true;
                        break;
                    }
                }
            }
        }
        // for (int i = 0; i < n; i++)
        // {
        //     DBG(dp[i]);
        // }
        return dp[0][n];
    }

    bool solve2(int n, int x, int[] a) {
        var liml = new int[n];
        var limr = new int[n];
        var bitl = new BIT[n];
        var bitr = new BIT[n];
        for (int i = 0; i < n; i++)
        {
            bitl[i] = new BIT(n - i);
            bitr[i] = new BIT(i + 1);
            for (int j = i, sum = 0; j < n; j++)
            {
                sum += a[j];
                if (sum <= x) {
                    limr[i] = j;
                }
                else break;
            }
            for (int j = i, sum = 0; j >= 0 ; j--)
            {
                sum += a[j];
                if (sum <= x) {
                    liml[i] = j;
                }
                else break;
            }
        }
        for (int d = 0; d < n; d++)
        {
            for (int l = 0; l + d < n; l++)
            {
                int r = l + d;
                if (bitr[r].sum(l, Math.Min(limr[l] + 1, r) + 1) + bitl[l].sum(Math.Max(liml[r] - 1, l) - l, r + 1 - l) == 0) {
                    // DBG(l, r, "False");
                    bitl[l].add(r - l, 1);
                    bitr[r].add(l, 1);
                }
            }
        }
        return bitr[n - 1].sum(1) == 0;
    }


}

class pair<T, U> : IComparable<pair<T, U>> {
    public T v1;
    public U v2;
    public pair() : this(default(T), default(U)) {}
    public pair(T v1, U v2) { this.v1 = v1; this.v2 = v2; }
    public int CompareTo(pair<T, U> a) {
        int c = Comparer<T>.Default.Compare(v1, a.v1);
        return c != 0 ? c : Comparer<U>.Default.Compare(v2, a.v2);
    }
    public override string ToString() => v1 + " " + v2;
    public void Deconstruct(out T a, out U b) { a = v1; b = v2; }
}
static class util {
    public static readonly int M = 1000000007;
    // public static readonly int M = 998244353;
    public static readonly long LM = 1L << 60;
    public static readonly double eps = 1e-11;
    public static void DBG(string a) => Console.Error.WriteLine(a);
    public static void DBG<T>(IEnumerable<T> a) => DBG(string.Join(" ", a));
    public static void DBG(params object[] a) => DBG(string.Join(" ", a));
    public static void Assert(bool cond) { if (!cond) throw new Exception(); }
    public static pair<T, U> make_pair<T, U>(T v1, U v2) => new pair<T, U>(v1, v2);
    public static int CompareList<T>(IList<T> a, IList<T> b) where T : IComparable<T> {
        for (int i = 0; i < a.Count && i < b.Count; i++)
            if (a[i].CompareTo(b[i]) != 0) return a[i].CompareTo(b[i]);
        return a.Count.CompareTo(b.Count);
    }
    public static bool inside(int i, int j, int h, int w) => i >= 0 && i < h && j >= 0 && j < w;
    static readonly int[] dd = { 0, 1, 0, -1 };
    // static readonly string dstring = "RDLU";
    public static P[] adjacents(int i, int j)
        => Enumerable.Range(0, dd.Length).Select(k => new P(i + dd[k], j + dd[k ^ 1])).ToArray();
    public static P[] adjacents(int i, int j, int h, int w)
        => Enumerable.Range(0, dd.Length).Select(k => new P(i + dd[k], j + dd[k ^ 1]))
                                         .Where(p => inside(p.v1, p.v2, h, w)).ToArray();
    public static P[] adjacents(this P p) => adjacents(p.v1, p.v2);
    public static P[] adjacents(this P p, int h, int w) => adjacents(p.v1, p.v2, h, w);
    public static Dictionary<T, int> compress<T>(this IEnumerable<T> a)
        => a.Distinct().OrderBy(v => v).Select((v, i) => new { v, i }).ToDictionary(p => p.v, p => p.i);
    public static Dictionary<T, int> compress<T>(params IEnumerable<T>[] a) => compress(a.Aggregate(Enumerable.Union));
    public static T[] inv<T>(this Dictionary<T, int> dic) {
        var res = new T[dic.Count];
        foreach (var item in dic) res[item.Value] = item.Key;
        return res;
    }
    public static void swap<T>(ref T a, ref T b) where T : struct { var t = a; a = b; b = t; }
    public static void swap<T>(this IList<T> a, int i, int j) where T : struct { var t = a[i]; a[i] = a[j]; a[j] = t; }
    public static T[] copy<T>(this IList<T> a) {
        var ret = new T[a.Count];
        for (int i = 0; i < a.Count; i++) ret[i] = a[i];
        return ret;
    }
}

class Scan {
    StreamReader sr;
    public Scan() { sr = new StreamReader(Console.OpenStandardInput()); }
    public Scan(string path) { sr = new StreamReader(path); }
    public int Int => int.Parse(Str);
    public long Long => long.Parse(Str);
    public double Double => double.Parse(Str);
    public string Str => sr.ReadLine().Trim();
    public pair<T, U> Pair<T, U>() {
        T a; U b;
        Multi(out a, out b);
        return new pair<T, U>(a, b);
    }
    public P P => Pair<int, int>();
    public int[] IntArr => StrArr.Select(int.Parse).ToArray();
    public long[] LongArr => StrArr.Select(long.Parse).ToArray();
    public double[] DoubleArr => StrArr.Select(double.Parse).ToArray();
    public string[] StrArr => Str.Split(new[]{' '}, StringSplitOptions.RemoveEmptyEntries);
    bool eq<T, U>() => typeof(T).Equals(typeof(U));
    T ct<T, U>(U a) => (T)Convert.ChangeType(a, typeof(T));
    T cv<T>(string s) => eq<T, int>()    ? ct<T, int>(int.Parse(s))
                       : eq<T, long>()   ? ct<T, long>(long.Parse(s))
                       : eq<T, double>() ? ct<T, double>(double.Parse(s))
                       : eq<T, char>()   ? ct<T, char>(s[0])
                                         : ct<T, string>(s);
    public void Multi<T>(out T a) => a = cv<T>(Str);
    public void Multi<T, U>(out T a, out U b)
    { var ar = StrArr; a = cv<T>(ar[0]); b = cv<U>(ar[1]); }
    public void Multi<T, U, V>(out T a, out U b, out V c)
    { var ar = StrArr; a = cv<T>(ar[0]); b = cv<U>(ar[1]); c = cv<V>(ar[2]); }
    public void Multi<T, U, V, W>(out T a, out U b, out V c, out W d)
    { var ar = StrArr; a = cv<T>(ar[0]); b = cv<U>(ar[1]); c = cv<V>(ar[2]); d = cv<W>(ar[3]); }
    public void Multi<T, U, V, W, X>(out T a, out U b, out V c, out W d, out X e)
    { var ar = StrArr; a = cv<T>(ar[0]); b = cv<U>(ar[1]); c = cv<V>(ar[2]); d = cv<W>(ar[3]); e = cv<X>(ar[4]); }
}

class BIT {
    int n;
    Number[] bit;
    public BIT(int n) {
        this.n = n;
        bit = new Number[n];
    }
    public void add(int j, Number w) {
        for (int i = j; i < n; i |= i + 1)
            bit[i] += w;
    }
    public Number at(int j) => sum(j, j + 1);
    // [0, j)
    public Number sum(int j) {
        Number ret = 0;
        for (int i = j - 1; i >= 0; i = (i & i + 1) - 1) ret += bit[i];
        return ret;
    }
    // [j, k)
    public Number sum(int j, int k) => sum(k) - sum(j);
}