#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

typedef long long ll;

int main()
{
	int W, H, N; vector<int> S, K;
	cin >> W >> H >> N;
	S.resize(N); K.resize(N);
	for (int i = 0; i < N; ++i)
		cin >> S[i] >> K[i];

	sort(S.begin(), S.end());
	auto it = unique(S.begin(), S.end());
	S.erase(it, S.end());
	sort(K.begin(), K.end());
	it = unique(K.begin(), K.end());
	K.erase(it, K.end());

	cout << (S.size() * H + K.size() * W) - S.size() * K.size() - N << endl;

	return 0;
}