#include <iostream>
#include <vector>
using namespace std;

bool cols[20000];
bool rows[20000];
bool top[40000];
bool bottom[40000];

int X, Y, N;

void init() {
	for(int i = 0; i < 20000; i++) {cols[i] = true; rows[i] = true;}
	for(int i = 0; i < 40000; i++) {top[i] = true; bottom[i] = true;}
}

int getTop(int x, int y) {
	return x + y;
}

int getBottom(int x, int y) {
	return x + (Y - y);
}

int pocetNeohrozenych()
{
	int count = 0;
	for(int i = 0; i < X; i++) {
		for(int j = 0; j < Y; j++) {
			if(cols[i] && rows[j] && top[getTop(i, j)] && bottom[getBottom(i, j)]) 
				count++;
		}
	}
	return count;
}
int main(){
	int x, y;
	
	cin >> X >> Y >> N;
	
	while(!(X == 0 && Y == 0 && N == 0))
	{
		init();
		
		for(int i = 0; i < N; i++) {
			cin >> x >> y;
			x--;
			y--;
			
			cols[x] = false;
			rows[y] = false;
			top[getTop(x, y)] = false;
			bottom[getBottom(x, y)] = false;
		}
		
		cout << pocetNeohrozenych();
		
		cin >> X >> Y >> N;
	}
	
	return 0;
}