using System;
using System.Collections.Generic;
using static System.Console;
using System.Linq;

class yuki320
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static void Main()
    {
        var c = NList;
        var (n, k) = (c[0], c[1]);
        var a = NList;
        var b = NList;

        var aisgood = new (int pos, int val)[n];
        for (var i = 0; i < n; ++i) aisgood[i] = (i, a[i] - b[i]);
        Array.Sort(aisgood, (l, r) => r.val.CompareTo(l.val));

        var res = Enumerable.Repeat('B', n).ToArray();
        for (var i = 0; i < k; ++i) res[aisgood[i].pos] = 'A';

        WriteLine(string.Concat(res));
    }
}