using System.Linq;
using System;

public class P
{
    public int amb { get; set; }
    public int id { get; set; }
}

public class Hello
{
    static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var n = int.Parse(line[0]);
        var k = int.Parse(line[1]);
        line = Console.ReadLine().Trim().Split(' ');
        var a = Array.ConvertAll(line, int.Parse);
        line = Console.ReadLine().Trim().Split(' ');
        var b = Array.ConvertAll(line, int.Parse);
        var ps = new P[n];
        var ans = new char[n];
        for (int i = 0; i < n; i++)
        {
            ps[i] = new P { id = i, amb = a[i] - b[i] };
            ans[i] = 'B';
        }
        getAns(n, k, ps, ans);
    }
    static void getAns(int n, int k, P[] ps, char[] ans)
    {
        foreach (var x in ps.OrderByDescending(x => x.amb).Take(k))
            ans[x.id] = 'A';
        Console.WriteLine(new string(ans));
    }
}