#include "bits/stdc++.h"
using namespace std;

int main() {
	long long W, H, N;
	set<long long> SW, SH;
	cin >> W >> H >> N;
	for (int i = 0; i < N; i++) {
		int S, K;
		cin >> S >> K;
		SW.insert(S);
		SH.insert(K);
	}
	cout << SW.size() * H + SH.size() * W - SW.size() * SH.size() - N << endl;
}