#include <bits/stdc++.h>
using namespace std;
void solve() {
  int n, m, k;
  cin >> n >> m >> k;
  vector<int> x(n);
  for (int i = 0; i < n; i++) cin >> x[i];
  vector<pair<int, int> > y(m);
  for (int i = 0; i < m; i++) cin >> y[i].first, y[i].second = i + 1;
  sort((x).begin(), (x).end());
  sort((y).begin(), (y).end());
  int xidx = 0;
  while (xidx < n) {
    if (x[xidx] < xidx / k) {
      cout << -1;
      return;
    }
    xidx += k;
  }
  reverse((y).begin(), (y).end());
  int mina = 0;
  int maxa = m + 1;
  while (maxa - mina > 1) {
    int mid = mina + (maxa - mina) / 2;
    vector<int> newarr((x).begin(), (x).end());
    vector<int> newarr2(mid);
    for (int i = 0; i < mid; i++) {
      newarr2[i] = y[i].first;
    }
    reverse((newarr2).begin(), (newarr2).end());
    vector<int> ansarr((int)newarr.size() + (int)newarr2.size());
    merge((newarr).begin(), (newarr).end(), (newarr2).begin(), (newarr2).end(),
          ansarr.begin());
    ;
    int num = n + mid;
    bool isGood = 1;
    int idx = 0;
    while (idx < num) {
      if (ansarr[idx] < idx / k) isGood = 0;
      idx += k;
    }
    if (isGood) {
      mina = mid;
    } else {
      maxa = mid;
    }
  }
  cout << mina << '\n';
  for (int i = 0; i < mina; i++) {
    cout << y[i].second << " ";
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int t = 1;
  while (t--) {
    solve();
  }
  return 0;
}
