#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(void){
    int x, y, n, xs, ys;
    int polex[20010], poley[20010], poled1[40020], poled2[40020];
    while (1==1){
	scanf("%d %d %d", &x, &y, &n);
	memset(polex, 0, sizeof(polex));
	memset(poley, 0, sizeof(poley));
	memset(poled1, 0, sizeof(poled1));
	memset(poled2, 0, sizeof(poled2));
	if ((x==0)&&(y==0)&&(n==0)) return 0;
	for (int i=0;i<n; i++){
	    scanf("%d %d", &xs, &ys);
	    polex[xs] = 1;
	    poley[ys] = 1;
	    poled1[xs-ys+20000] = 1;
	    poled2[xs+ys] = 1;
	}
	int pocet = 0;
	for (int i=1; i<=x; i++){
	    for (int j=1; j<=y; j++){
		if (polex[i]+ poley[j] + poled1[i-j+20000] + poled2[i+j] == 0) pocet++;
	    }
	}
	printf("%d\n", pocet);
    }
    return 0;
}