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

int main() {
	int a, b, n;
	int k, j ,l, i;
	int x, y;
	char **p;
	p = (char **)malloc(20000*sizeof(char*));
	for(j = 0; j < 20000; j++) 
		p[j] = (char*)malloc(20000*sizeof(char));
	while(1) {
		scanf("%d %d %d", &a,&b,&n);
		if (a == 0 && b==0 && n==0) return 0;
		for(k = 0; k < a; k++)
		for(j = 0; j < b; j++) p[k][j] = 0;
		for(i = 0; i < n; i++) {
			scanf("%d %d", &x,&y);
			x--; y--;
			for(j = 0; j < a; j++) p[j][y] = 1;
			for(j = 0; j < b; j++) p[x][j] = 1;
			j = x; k = y;
			while(j > 0 && k > 0) p[--j][--k] = 1;
			j = x; k = y;
			while(j < a && k < b) p[++j][++k] = 1;
			j = x; k = y;
			while(j < a && k > 0) p[++j][--k] = 1;
			j = x; k = y;
			while(j > 0 && k < b) p[--j][++k] = 1;
		}
		l = 0;
		for(k = 0; k < a; k++) {
			for(j = 0; j < b; j++) {
				if(p[k][j] == 0) l++;
			}
		}
		printf("%d\n", l);
	}
	return 0;
}