#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<vector>
#include<queue>
#include<set>
#include<map>
#include<utility>
#include<sstream>
#include<cctype>
#include<cmath>
#include<algorithm>
using namespace std;

#define ALL(x) (x).begin(),(x).end()
#define RALL(x) (x).rbegin(), (x).rend()
#define rev(i,n) for(int (i)=(n-1);(i)>=0;(i)--)
#define repp(i,n) for(int (i)=1;(i)<=(n);(i)++)
#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)
#define rev(i,n) for(int (i)=(n-1);(i)>=0;(i)--)
#define clr(a) memset((a), 0 ,sizeof(a))


typedef pair<int,int> P;
typedef vector<pair<int,string> > pii;
typedef map<string,int> mi;



int main(){
	long long w,h,n,s,k,ans=0;
	set<int> se,se2;
	cin >> w >> h >> n;
	for(int i=0;i<n;i++){
		cin >> s >> k;
		se.insert(s);
		se2.insert(k);
	}
	
	ans+=se.size()*h;
	ans+=se2.size()*w;
	ans-=se.size()*se2.size();
	ans-=n;
	cout << ans << endl;
	return 0;
}