#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define rep1(i,n) for(int i=1;i<=(int)(n);i++)
#define all(c) c.begin(),c.end()
#define pb push_back
#define fs first
#define sc second
#define show(x) cout << #x << " = " << x << endl
#define chmin(x,y) x=min(x,y)
#define chmax(x,y) x=max(x,y)
using namespace std;
typedef long long ll;
set<int> as,bs;
int main(){
	int H,W,N;
	cin>>H>>W>>N;
	rep(i,N){
		int a,b;
		cin>>a>>b;
		as.insert(a);
		bs.insert(b);
	}
	ll X=as.size(),Y=bs.size();
	cout<<X*W+Y*H-X*Y-N<<endl;
}