#include <iostream>
#include <string.h>

using namespace std;

int main() {
    while (cin) {
	int w,h,n;
	cin >> w >> h >> n;
	if (w==0 && h==0 && n==0) break;
	bool wp[w];
	bool hp[h];
	bool pd[w+h-1], ld[w+h-1];
	memset(wp,0,w);
	memset(hp,0,h);
	memset(pd,0,w+h-1);
	memset(ld,0,w+h-1);
	for (int i = 0; i < n; i++) {
	    int x,y;
	    cin >> x >> y;
	    x--; y--;
	    wp[x] = true;
	    hp[y] = true;
	    pd[x+(h-y-1)] = true;
	    ld[(w-x-1)+(h-y-1)] = true;
	}
	
	int sz = w*h/8+1;
	unsigned char poile[sz];
	memset(poile,0,sz);
	
	int volny = 0;
	for (int y = 0; y < h; y++) {
	    for (int x = 0; x < w; x++) {
		if (wp[x]) continue;
		if (hp[y]) continue;
    	        if (pd[x+(h-y-1)]) continue;
	        if (ld[(w-x-1)+(h-y-1)]) continue;
		volny++;
	    }
	}
	cout << volny << endl;
	
    }
    return 0;
}