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

int main() {
  ll w,h,n;cin>>w>>h>>n;
  set<int> tate,yoko;
  for(int i=0;i<n;i++){
    int s,k;cin>>s>>k;
    tate.insert(s);
    yoko.insert(k);
  }
  cout<<h*w-(w-tate.size())*(h-yoko.size())-n<<endl;
}