#include<stdio.h>
#include <vector>
#include <list>
#include <map>
#include <set>
#include<unordered_set>
#include <queue>
#include <stack>
#include <algorithm>
#include <sstream>
#include <iostream>
#include <string>

using namespace std;

int main() {

	int W, H, N, S[105], K[105];
	cin >> W >> H >> N;
	for (int i = 0; i < N; i++) {
		cin >> S[i] >> K[i];
	}

	long long  ans = 0;
	unordered_set<int> s1, s2;

	for (int i = 0; i < N; i++) {
		s1.insert(S[i]);
		s2.insert(K[i]);
	}

	ans = W*s2.size() + H*s1.size() - s1.size()*s2.size() - N;

	cout << ans << endl;

	return 0;
}