#include<bits/stdc++.h>
using namespace std;

using ll=long long;

int main(){cin.tie(0);ios::sync_with_stdio(false);
	ll W,H;cin>>W>>H;
	int N;cin>>N;
	vector<ll>x(N),y(N);
	ll mx=2e9,MX=-2e9;
	ll my=2e9,MY=-2e9;
	ll mp=2e9,MP=-2e9;
	ll mm=2e9,MM=-2e9;
	bool o=true;
	for(int i=0;i<N;++i){
		cin>>x[i]>>y[i];
		mx=min(mx,x[i]);
		MX=max(MX,x[i]);
		my=min(my,y[i]);
		MY=max(MY,y[i]);
		mp=min(mp,x[i]+y[i]);
		MP=max(MP,x[i]+y[i]);
		mm=min(mm,x[i]-y[i]);
		MM=max(MM,x[i]-y[i]);
		o&=(x[i]+y[i])%2==(x[0]+y[0])%2;
	}
	ll z=0;
	if(o){
		for(int _=0;_<4;++_){
			if(N==2){
				if(mp==MP){
					z=max(z,mx*my+(W-MX+1)*(H-MY+1)+MX-mx-1);
				}else if(MX-mx<MY-my){
					z=max(z,W);
				}
			}else{
				bool a=mp==MP;
				bool b=true;
				bool c=MP-mp>=MM-mm;
				bool d=c;
				bool e=MP-mp==MM-mm;
				for(int i=0;i<N;++i){
					b&=x[i]+y[i]==MP||x[i]-y[i]==MM;
					c&=x[i]+y[i]==MP||x[i]+y[i]==mp;
					d&=x[i]+y[i]==MP||x[i]+y[i]==mp||x[i]-y[i]==MM;
					e&=x[i]+y[i]==MP||x[i]+y[i]==mp||x[i]-y[i]==MM||x[i]-y[i]==mm;
				}
				if(a)z=max(z,mx*my+(W-MX+1)*(H-MY+1));
				if(b)z=max(z,mx);
				if(c)z=max(z,((MP-mp)-(MM-mm))/2+1);
				if(d)z=max(z,1ll);
				if(e)z=max(z,1ll);
			}
			for(int i=0;i<N;++i){
				ll t=x[i];
				x[i]=H-y[i]+1;
				y[i]=t;
			}
			swap(W,H);
		}
	}
	cout<<z<<"\n";
	return 0;
}