#include <iostream>
#include <vector>
#include <algorithm>
#include <atcoder/modint>
#include <atcoder/fenwicktree>
using namespace std;
using i64 = int64_t;
using u64 = uint64_t;
#define rep(i,n) for(int i=0; i<(n); i++)


int H,W,N;

vector<int> solve(vector<pair<int,int>> P){
  vector<int> ans;
  vector<vector<int>> E(W);
  vector<vector<int>> D(H);
  rep(i,N){
    auto p = P[i];
    E[p.second].push_back(i);
    D[p.first].push_back(i);
  }
  rep(x,H){
    vector<int> YI;
    for(auto i : D[x]){
      int y = P[i].second;
      if(E[y].size() >= 2) YI.push_back(i);
    }
    if(YI.size() < 2) continue;
    ans.resize(4);
    ans[1] = YI[0];
    ans[2] = YI[1];
    for(int e : E[P[YI[0]].second]) if(e != YI[0]) ans[0] = e;
    for(int e : E[P[YI[1]].second]) if(e != YI[1]) ans[3] = e;
    return ans;
  }
  return ans;
}

int main() {
  cin >> H >> W >> N;
  vector<pair<int,int>> P(N);
  rep(i,N){
    int y,x; cin >> y >> x; y--; x--;
    P[i] = {y,x};
  }
  vector<int> ans;
  //rep(t,2){
    //rep(i,N) swap(P[i].first,P[i].second);
    //swap(H,W);
    ans = solve(P);
    //if(!ans.empty()) break;
  //}
  if(ans.empty()){
    cout << "-1\n";
  }
  else{
    cout << "4\n";
    rep(i,4){
      if(i) cout << " ";
      cout << (ans[i]+1);
    }
    cout << "\n";
  }
  return 0;
}


struct ios_do_not_sync{
  ios_do_not_sync(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
  }
} ios_do_not_sync_instance;