#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000001


int main(){
	
	long long w,h;
	cin>>w>>h;
	
	set<int> sw,sh;
	int n;
	cin>>n;
	rep(i,n){
		int a,b;
		cin>>a>>b;
		sw.insert(a);
		sh.insert(b);
	}
	
	long long ans = w * sh.size();
	ans += h * sw.size();
	ans -= sh.size() * sw.size();
	ans -= n;
	
	cout<<ans<<endl;
	
	return 0;
}