#include <bits/stdc++.h>
using namespace std;
int main(){
  int N, K;
  cin >> N >> K;
  vector<int> A(N);
  for (int i = 0; i < N; i++){
    cin >> A[i];
  }
  vector<int> B(N);
  for (int i = 0; i < N; i++){
    cin >> B[i];
  }
  string S;
  int cnt = 0;
  for (int i = 0; i < N; i++){
    if (A[i] > B[i]){
      S += 'A';
      cnt++;
    } else {
      S += 'B';
    }
  }
  if (cnt < K){
    vector<pair<int, int>> P1;
    for (int i = 0; i < N; i++){
      if (S[i] == 'B'){
        P1.push_back(make_pair(B[i] - A[i], i));
      }
    }
    sort(P1.begin(), P1.end());
    for (int i = 0; i < K - cnt; i++){
      S[P1[i].second] = 'A';
    }
  } else if (cnt > K){
    vector<pair<int, int>> P2;
    for (int i = 0; i < N; i++){
      if (S[i] == 'A'){
        P2.push_back(make_pair(A[i] - B[i], i));
      }
    }
    sort(P2.begin(), P2.end());
    for (int i = 0; i < cnt - K; i++){
      S[P2[i].second] = 'B';
    }
  }
  cout << S << endl;
}