#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <utility>
#include <set>

using namespace std;

int main() {
	int w, h, n;
	cin >> w >> h >> n;

	set<int> used_w, used_h;
	int s, k;
	for (int i = 0; i < n; i++) {
		cin >> s >> k;
		used_w.insert(s);
		used_h.insert(k);
	}

	long long total = (long long) w * h - (w - used_w.size()) * (h - used_h.size()) - n;
	cout << total << endl;
	return 0;
}