#include<stdio.h>
#include <vector>
#include <list>
#include <map>
#include <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;
	set<int> s1, s2;
	for (int i = 0; i < W; i++) {
		int cnt = 0;
		bool flag = false;
		for (int j = 0; j<N; j++) {
			if (S[j] == i + 1) {
				cnt++;
				flag = true;
			}
			s2.insert(K[j]);
		}
		if (flag) {
			ans += H - cnt;
			s1.insert(i + 1);
			flag = false;
		}
	}

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

	cout << ans << endl;

	return 0;
}