#include <cstdlib>
#include <iostream>

using namespace std;

class queen{
public:
    int x;
    int y;
    queen(){
    x = 0;
    y = 0;
    }
};

int main(int argc, char** argv){
    while(1){
    int x, y, pocet_q;
    int soucet = 0;
    cin >> x >> y >> pocet_q;
    if(x==0 && y==0 && pocet_q == 0){
	return 0;
    }
    queen kralovny[pocet_q];
    for (int i = 0; i<pocet_q;i++){
	int poz_x, poz_y;
	cin >> poz_x >> poz_y;
	kralovny[i].x = poz_x;
	kralovny[i].y = poz_y;
    }
    
    
    for (int i = 1; i<=x;i++){
	for (int j = 1; j<=y; j++){
	    for (int k=0;k<pocet_q;k++){
		if (i==kralovny[k].x){
		    soucet++;
		    break;
		}
		if (j==kralovny[k].y){
		    soucet++;
		    break;
		}
		if (abs(i - kralovny[k].x) == abs(j - kralovny[k].y)){
		    soucet++;
		    break;
		}
	    }
	}
    }
    
    cout << x*y - soucet << endl;
    }
    return 0;
}