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

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        int k = sc.nextInt();
        Cosme[] cosmes = new Cosme[n];
        for (int i = 0; i < n; i++) {
            cosmes[i] = new Cosme(i, sc.nextInt());
        }
        for (int i = 0; i < n; i++) {
            cosmes[i].value -= sc.nextInt();
        }
        Arrays.sort(cosmes);
        boolean[] ans = new boolean[n];
        for (int i = 0; i < n - k; i++) {
            ans[cosmes[i].idx] = true;
        }
        StringBuilder sb = new StringBuilder();
        for (boolean x : ans) {
            if (x) {
                sb.append("B");
            } else {
                sb.append("A");
            }
        }
        System.out.println(sb);
    }
    
    static class Cosme implements Comparable<Cosme> {
        int idx;
        int value;
        
        public Cosme(int idx, int value) {
            this.idx = idx;
            this.value = value;
        }
        
        public int compareTo(Cosme another) {
            return value - another.value;
        }
    }
}
class Utilities {
    static String arrayToLineString(Object[] arr) {
        return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n"));
    }
    
    static String arrayToLineString(int[] arr) {
        return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new));
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public int[] nextIntArray() throws Exception {
        return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
    
}