#include<bits/stdc++.h>
using namespace std;
using Int = long long;
template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}

//INSERT ABOVE HERE
signed main(){
  Int w,h,n;
  cin>>w>>h>>n;
  
  vector<Int> vx(n),vy(n);
  for(Int i=0;i<n;i++) cin>>vx[i]>>vy[i];

  set<Int> sx,sy;
  for(Int x:vx) sx.emplace(x);
  for(Int y:vy) sy.emplace(y);

  Int ans=sx.size()*h+sy.size()*w-sx.size()*sy.size()-n;

  cout<<ans<<endl;
  return 0;
}