#include<cstdio>
#include<iostream>
#include<algorithm>
#include<string>
#include<queue>
#include<vector>
#include<functional>
#include<cmath>
#include<map>
#include<stack>
#include<set>
#include<numeric>
#include<limits>

#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()

using namespace std;
typedef long long ll;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef pair<ll, string> pls;

bool mark[1000001];
bool num[1000001];

int main()
{
	ll H, W, h = 0, w = 0;
	int n;
	cin >> H >> W >> n;
	for (int i = 0; i < n; i++) {
		int s, k;
		cin >> s >> k;
		if (mark[s] == false)h++;
		if (num[k] == false)w++;
		mark[s] = num[k] = true;
	}
	cout << h*W + w*H - h*w - n << endl;
	return 0;
}