#include <bits/stdc++.h>
#define syosu(x) fixed<<setprecision(x)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> P;
typedef pair<double,double> pdd;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<long double> vd;
typedef vector<vd> vvd;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<string> vs;
typedef vector<P> vp;
typedef vector<vp> vvp;
typedef vector<pll> vpll;
typedef pair<int,P> pip;
typedef vector<pip> vip;
const int inf=1<<30;
const ll INF=1ll<<60;
const double pi=acos(-1);
const double eps=1e-8;
const ll mod=1e9+7;
const int dx[4]={0,1,0,-1},dy[4]={1,0,-1,0};

ll w,h,n;
vi a,b;

int main(){
	cin>>w>>h>>n;
	for(int i=0;i<n;i++){
		int A,B;
		cin>>A>>B;
		a.push_back(A);
		b.push_back(B);
	}
	sort(a.begin(),a.end());
	a.erase(unique(a.begin(),a.end()),a.end());
	sort(b.begin(),b.end());
	b.erase(unique(b.begin(),b.end()),b.end());
	ll A=a.size(),B=b.size();
	cout<<A*h+B*w-A*B-n<<endl;
}