#include <bits/stdc++.h>

using namespace std;

#define rep(i, n) for (int i = 0; i < (int)n; ++i)
#define FOR(i, a, b) for (int i = a; i < (int)b; ++i)
#define rrep(i, n) for (int i = ((int)n - 1); i >= 0; --i)

using ll = long long;
using ld = long double;

__attribute__((unused)) const ll INF = 1e18;
__attribute__((unused)) const int Inf = 1e9;
__attribute__((unused)) const double EPS = 1e-9;
__attribute__((unused)) const ll MOD = 1000000007;

int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(0);
  int n, k;
  cin >> n >> k;
  vector<ll> a(n), b(n);
  rep(i, n) cin >> a[i];
  rep(i, n) cin >> b[i];
  vector<pair<ll, int>> d(n);
  rep(i, n) {
    d[i].first = a[i] - b[i];
    d[i].second = i;
  }
  string res(n, 'B');
  sort(d.rbegin(), d.rend());
  rep(i, k) { res[d[i].second] = 'A'; }
  cout << res << endl;

  return 0;
}