#include<bits/stdc++.h>
namespace {
#include<atcoder/all>
using namespace std;
using namespace atcoder;
#define rep(i,n)for (int i = 0; i < int(n); ++i)
#define rrep(i,n)for (int i = int(n)-1; i >= 0; --i)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
template<class T> void chmax(T& a, const T& b) { a = max(a, b); }
template<class T> void chmin(T& a, const T& b) { a = min(a, b); }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, k;
  cin >> n >> k;
  VI a(n), b(n);
  rep(i, n) cin >> a[i];
  rep(i, n) cin >> b[i];
  string ans(n, 'B');
  priority_queue<P> q;
  rep(i, n) q.emplace(a[i] - b[i], i);
  rep(_, k) ans[q.top().second] = 'A', q.pop();
  cout << ans << '\n';
}