package main

import . "fmt"
import bf "bufio"
import . "os"
import . "sort"

func main() {
	rd:=bf.NewReader(Stdin)
	var n,k int
	Fscan(rd,&n,&k)
	type Item struct { a, b, c, i int }
	xs := make([]*Item, n)
	for i := range xs {
		xs[i] = new(Item)
		xs[i].i = i
		Fscan(rd,&xs[i].a)
	}
	for _, x := range xs {
		Fscan(rd,&x.b)
		x.c = x.b - x.a
	}
	Slice(xs, func(i, j int) bool {
		return xs[i].c < xs[j].c
	})
	ans := make([]byte, n)
	for i, x := range xs {
		if i < k {
			ans[x.i] = 'A'
		} else {
			ans[x.i] = 'B'
		}
	}
	Println(string(ans))
}