#include <bits/stdc++.h>
using namespace std;

signed main(){
  int W, H, N; cin >> W >> H >> N;
  set< int > suit, val;
  for( int i = 0; i < N; ++i ){
    int S, K; cin >> S >> K;
    suit.insert( S );
    val.insert( K );
  }
  int ans = suit.size() * H + val.size() * W - suit.size() * val.size() - N;
  cout << ans << endl;
  return 0;
}