#include <iostream>
#include <cmath>
#include <vector>

using namespace std;

inline int iabs(int x) {
	return x > 0 ? x : -x;
}

struct Pair {
	
	Pair(int x, int y) {
		first = x;
		second = y;
	}
	
	int first;
	int second;
};

int main() {
	
	int x = 42;
	int y = 42;
	int n = 42;

	bool rows[20000];
	bool cols[20000];

	cin >> x >> y >> n;

	while(x || y || n) {

		int kx;
		int ky;

		vector<Pair> queens;

		int free = 0;

		for(int i = 0; i< 20000; i++) rows[i] = cols[i] = false;


		for(int i = 0; i < n; i++)		 {
			cin >> kx >> ky;			
			queens.push_back(Pair(kx -1,ky -1));
			rows[kx-1] = true;
			cols[ky-1] = true;
		}



		if(n > 0) {
			for(int i = 0; i < x; i++) {
				if(rows[i]) continue;
				for(int j = 0; j < y; j++) {
					if(cols[j]) continue;
									
					bool flag = false;
					for(int k = 0; k < n; k++) {					
						if(iabs(i - queens[k].first) == iabs(j - queens[k].second)) {
							flag = true;
							break;
						}
					}

					if(!flag) free++;

				}
			}
		}else {
			free = x*y;
		}
		
		cout << free << endl;

		cin >> x >> y >> n;

		queens.clear();
	}

	return 0;
}