/* -*- coding: utf-8 -*-
 *
 * 1724.cc:  No.1724 [Cherry 3rd Tune A] Lápiz labial de Sonia - yukicoder
 */

#include<cstdio>
#include<algorithm>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 200000;

/* typedef */

typedef pair<int,int> pii;

/* global variables */

int as[MAX_N], bs[MAX_N];
pii ps[MAX_N];
char s[MAX_N + 4];

/* subroutines */

/* main */

int main() {
  int n, k;
  scanf("%d%d", &n, &k);
  for (int i = 0; i < n; i++) scanf("%d", as + i);
  for (int i = 0; i < n; i++) scanf("%d", bs + i);

  for (int i = 0; i < n; i++) ps[i] = pii(as[i] - bs[i], i);
  sort(ps, ps + n, greater<pii>());
  //for (int i = 0; i < n; i++) printf("%d,%d ", ps[i].first, ps[i].second);
  //putchar('\n');

  fill(s, s + n, 'B');
  for (int i = 0; i < k; i++) s[ps[i].second] = 'A';

  puts(s);
  return 0;
}