#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long int n, m, k;
  cin >> n >> m >> k;
  vector<pair<long long int, long long int> > F(n), S(m);
  long long int maxDay = 0;
  for (long long int i = 0; i < n; i++) {
    cin >> F[i].first;
    F[i].second = i + 1;
    maxDay = max(maxDay, F[i].first);
  }
  for (long long int i = 0; i < m; i++) {
    cin >> S[i].first;
    S[i].second = i + 1;
  }
  long long int f_i = 0, s_i = 0;
  sort(F.begin(), F.begin() + F.size());
  sort(S.begin(), S.begin() + S.size());
  vector<long long int> res;
  for (long long int i = 0; i <= maxDay; i++) {
    long long int use = 0;
    while (use < k && f_i < F.size() && F[f_i].first == i) {
      f_i++;
      use++;
    }
    if (use == k && f_i < F.size() && F[f_i].first == i) {
      cout << "-1";
      return 0;
    }
    while (s_i < S.size() && S[s_i].first < i) s_i++;
    while (use < k && s_i < S.size() && S[s_i].first >= i) {
      res.push_back(S[s_i].second);
      use++;
      s_i++;
    }
    while (use < k && f_i < F.size() && F[f_i].first > i) {
      use++;
      f_i++;
    }
  }
  for (long long int i = maxDay + 1; s_i < S.size(); i++) {
    long long int use = 0;
    while (s_i < S.size() && S[s_i].first < i) s_i++;
    while (use < k && s_i < S.size() && S[s_i].first >= i) {
      res.push_back(S[s_i].second);
      s_i++;
      use++;
    }
  }
  cout << res.size() << "\n";
  for (auto x : res) cout << x << " ";
}
