import java.io.*;
import java.util.*;

class Main
{
    public static void main(String args[])throws Exception
    {
        BufferedReader bu=new BufferedReader(new InputStreamReader(System.in));
        StringBuilder sb=new StringBuilder();
        String s[]=bu.readLine().split(" ");
        int n=Integer.parseInt(s[0]),k=Integer.parseInt(s[1]);
        int i,a[]=new int[n],b[]=new int[n];

        s=bu.readLine().split(" ");
        for(i=0;i<n;i++) a[i]=Integer.parseInt(s[i]);
        PriorityQueue<int[]> pq=new PriorityQueue<>(new Comparator<int[]>() {
            @Override
            public int compare(int[] o1, int[] o2) {
                if(o1[0]<o2[0]) return 1;
                else return -1;
            }});
        s=bu.readLine().split(" ");
        for(i=0;i<n;i++)
        {
            b[i]=Integer.parseInt(s[i]);
            pq.add(new int[]{a[i]-b[i],i});
        }

        int ans[]=new int[n];
        while(k-->0) ans[pq.poll()[1]]=1;
        for(i=0;i<n;i++)
        if(ans[i]==0) sb.append("B");
        else sb.append("A");
        System.out.println(sb);
    }
}