#include <bits/stdc++.h>

using namespace std;

int main() {
    long long n, m, k;
    cin >> n >> m >> k;

    int x[k+2];
    int y[k+2];

 for (int i=0;i<k;i++) {
     cin>>x[i]>>y[i];
 }
 x[k]=0;
 y[k]=0;
 x[k+1]=n+1;
 y[k+1]=m+1;
 sort(x,x+k+2);
  sort(y,y+k+2);
  int ans1=0;
  int ans2=0;
  for (int i=0;i<k+1;i++) {
      ans1+=(x[i+1]-x[i]>=2);
      ans2+=(y[i+1]-y[i]>=2);
  }
  cout<<ans1*ans2;


}