#include <bits/stdc++.h>
using namespace std;
const int N=1000000;
long long w,h,ans;
int n,a,b,ww[N+10],hh[N+10],wc,hc;
int main(){
	cin>>w>>h;
	cin>>n;
	memset(ww,0,sizeof(ww));
	memset(hh,0,sizeof(hh));
	for(int i=0;i<n;++i){
		cin>>a>>b;
		ww[a]=hh[b]=1;
	}
	wc=hc=0;
	for(int i=0;i<N;++i){
	    if(ww[i]) ++wc;
	    if(hh[i]) ++hc;
    }
	cout<<w*hc+h*wc-hc*wc-n<<endl;
    return 0;
}