#include <cstdio>
#include <iostream>

using namespace std;

#define VEL 20000

void obsad(bool **pole, int x, int y, int a, int b) {
	pole[a][b] = true;
	for (int i = 0; i < x; i++) {
		pole[i][b] = true;
	}
	for (int i = 0; i < y; i++) {
		pole[a][i] = true;
	}
	int c, d;
	c = a;
	d = b;
	while (c >= 0 && d >= 0 && c < x && d < y) {
		pole[c][d] = true;
		c--;
		d--;
	}
	c = a;
	d = b;
	while (c >= 0 && d >= 0 && c < x && d < y) {
		pole[c][d] = true;
		c++;
		d--;
	}
	c = a;
	d = b;
	while (c >= 0 && d >= 0 && c < x && d < y) {
		pole[c][d] = true;
		c++;
		d++;
	}
	c = a;
	d = b;
	while (c >= 0 && d >= 0 && c < x && d < y) {
		pole[c][d] = true;
		c--;
		d++;
	}
}

int main() {
	int x, y, n;
	int a, b;
	bool **pole;
	do {
		cin >> x;
		cin >> y;
		cin >> n;
		if (x+y+n==0) {
			break;
		}

		pole = new bool*[VEL];
		for (int i = 0; i < x; i++) {
			pole[i] = new bool[VEL];
			for (int j = 0; j < y; j++) {
				pole[i][j] = false;
			}
		}

		// obsad
		for (int i = 0; i < n; i++) {
			cin >> a;
			cin >> b;
			obsad(pole, x, y, a-1, b-1);
		}

		/*for (int i = 0; i < x; i++) {
			for (int j = 0; j < y; j++) {
				cout << pole[i][j];
			}
			cout << endl;
		}*/

		// spocitej
		int cnt = 0;
		for (int i = 0; i < x; i++) {
			for (int j = 0; j < y; j++) {
				if (!pole[i][j]) {
					cnt++;
				}
			}
		}

		cout << cnt << endl;
	} while(true);
	return 0;
}