#include<iostream>
#include<vector>
#include<string>
#include<algorithm>	
#include<map>
#include<set>
#include<utility>
#include<cmath>
#include<cstring>
#include<queue>
#include<stack>
#include<cstdio>
#include<sstream>
#include<iomanip>
#include<assert.h>
#include<ctime>
#include<cstdlib>
#include<numeric>
using namespace std;
typedef long long ll;
#define loop(i,a,b) for(int i=a;i<b;i++)
#define rloop(i,a,b) for(int i=a;i>b;i--)
const int inf=1e8;
const ll INF=1e16;
#define MOD 1000000007
#define mod 1000000009

int main(){
	ll w,h;
	int n;
	cin>>w>>h>>n;
	ll s[n],k[n];
	loop(i,0,n){
		cin>>s[i]>>k[i];
	}
	sort(s,s+n);
	sort(k,k+n);
	vector< vector<ll> > kazu;
	ll m=k[0],cnt=1;
	ll temp[2];
	loop(i,1,n){
		if(k[i]==m){
			cnt++;
		}else{
			temp[0]=m;temp[1]=cnt;
			kazu.push_back(vector<ll>(temp,temp+2));
			cnt=1;m=k[i];
		}
	}
	temp[0]=m;temp[1]=cnt;
	kazu.push_back(vector<ll>(temp,temp+2));
	m=s[0],cnt=1;
	loop(i,1,n){
		if(s[i]!=m){
			cnt++;
			m=s[i];
		}
	}
	ll sum=0;
	loop(i,0,kazu.size()){
		sum+=w-kazu[i][1];
	}
	sum+=(h-kazu.size())*cnt;
	cout<<sum<<"\n";
}