#define KONST 20000
int radky_x[20001];
int sloupce_y[20001];
int uhl_p[40001];
int uhl_m[40001];

void work(int X, int Y, int N) {
	int i,j,k,l,x,y;
	for (i = 0; i < N; i++) {
		scanf("%i %i\n", &x, &y);
		radky_x[x]++;
		sloupce_y[y]++;
		uhl_p[x+y]++;
		uhl_m[x-y+KONST]++;
	}

	unsigned long long moznosti = 0;
	for (i = 1; i <= X; i++) {
		if (radky_x[i] == 0) {
			for (j = 1; j <= Y; j++) {
				if ((sloupce_y[j] == 0) && (uhl_p[j+i] == 0) && (uhl_m[i-j+KONST] == 0))
					moznosti++;
			}
		}
	}

	printf("%llu\n", moznosti);

}

int main() {

	int X = 0 ,Y = 0,Z = 0;
	while (1) {
		memset(radky_x, 0, sizeof(radky_x));
		memset(sloupce_y, 0, sizeof(sloupce_y));
		memset(uhl_p, 0, sizeof(uhl_p));
		memset(uhl_m, 0, sizeof(uhl_m));
		scanf("%i %i %i\n", &X, &Y, &Z);
		if ((X == 0) && (Y == 0) && (Z == 0)) break;
		work(X, Y, Z);
	}
	return 0;
}