#include<iostream>
#include<set>
#define int long long
using namespace std;

set<int> S, K;

signed main() {
	int i;
	int w, h, n;
	cin >> w >> h >> n;
	
	for( i = 0; i < n; i++ ) {
		int s, k;
		cin >> s >> k;
		S.insert(s);
		K.insert(k);
	}
	
	int Ssize = S.size();
	int Ksize = K.size();
	
	//cout << Ssize << " " << Ksize << " " << w << " " << h << " " << n << endl;
	cout << Ssize * h + Ksize * w - Ssize * Ksize - n << endl;
	return 0;
}