#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstdlib>
#include<iomanip>
#include<cstring>
#include<string>
#include<cmath>
#include<vector>
#include<queue>
#include<deque>
#include<set>
#include<map>
#include<utility>
#include<stack>

using namespace std;

int main(){
    vector<int> riadky,stlpce,d1,d2;
    int R,C,N,x,y;
    cin>>R>>C>>N;
    while(R){
	riadky.clear();
	stlpce.clear();
	d1.clear();
	d2.clear();
	riadky.resize(R);
	stlpce.resize(C);
	d1.resize(R+C);
	d2.resize(R+C);
	for (int i=0;i<N;i++){
	    scanf("%d %d ",&x,&y);
	    riadky[x-1]=1;
	    stlpce[y-1]=1;
	    d1[x+y-2]=1;
	    d2[x-y+C]=1;
	}
	int sucet=0;
	for (int i=0;i<R;i++){
	    if (riadky[i]==0){
		for (int j=0;j<C;j++){
		    if (stlpce[j]==0 && d1[i+j]==0 && d2[i-j+C]==0) sucet++;
		}
	    }
	}
	cout<<sucet<<endl;
	cin>>R>>C>>N;
    }
    return 0;
}