#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(ri,n) for(int ri = (int)(n-1); ri >= 0; ri--)
#define rep2(i,x,n) for(int i = (int)(x); i < (int)(n); i++)
#define rrep2(ri,x,n) for(int ri = (int)(n-1); ri >= (int)(x); ri--)
#define repit(itr,x) for(auto itr = x.begin(); itr != x.end(); itr++)
#define rrepit(ritr,x) for(auto ritr = x.rbegin(); ritr != x.rend(); ritr++)
#define ALL(x) x.begin(), x.end()
using ll = long long;
using namespace std;

int main() {
  int n, k;
  cin >> n >> k;
  vector<int> a(n);
  rep(i, n) cin >> a.at(i);
  vector<int> b(n);
  rep(i, n) cin >> b.at(i);
  vector<pair<int, int>> c(n);
  rep(i, n) {
    c.at(i) = {a.at(i)-b.at(i), i};
  }
  sort(ALL(c), greater<pair<int, int>>());
  string ans(n, ' ');
  int p = 0;
  for(auto [co, idx] : c) {
    if(p < k) ans.at(idx) = 'A';
    else ans.at(idx) = 'B';
    p++;
  }
  cout << ans << endl;
  return 0;
}