#include <iostream>
#include <vector>
#include <set>

using namespace std;

int main() {
	int w, h, n;
	cin >> w >> h >> n;
	vector<int> s(n), k(n);
	for (int i = 0; i < n; ++i) {
		cin >> s[i] >> k[i];
	}
	set<int> marks, numbers;
	for (int i = 0; i < n; ++i) {
		marks.insert(s[i]);
		numbers.insert(k[i]);
	}
	int markMatched = marks.size() * h;
	int numberMatched = numbers.size() * w;
	int result = markMatched + numberMatched
		- marks.size() * numbers.size() - n;
	cout << result << endl;
	return 0;
}