#include <iostream>

typedef long long ll;

int w, h, n;
bool isW[1000001], isH[1000001];
ll all;

int main(){
	std::cin >> w >> h >> n;
	all = w * h;

	for (int i = 0; i < n; i++){
		int a, b;
		std::cin >> a >> b;
		a--, b--;
		isW[a] = true;
		isH[b] = true;
	}

	int cntW = 0, cntH = 0;
	for (int i = 0; i < w; i++)if (!isW[i])cntW++;
	for (int i = 0; i < h; i++)if (!isH[i])cntH++;

	ll cnt = cntW * cntH;

	std::cout << all - cnt - n << std::endl;

	return 0;
}