#include<iostream>
#include<cstdio>
#include<algorithm>
#include<vector>
using namespace std;
int ans,tot,head,tail;
int m,n,q;
int main()
{    
     freopen("deleteit.in","r",stdin);
     freopen("deleteit.out","w",stdout);
	cin>>n>>m>>q;
	ans=m*n;
	for(int i=0;i<q;i++)
	{
		int x1,x2,y1,y2;
		cin>>x1>>y1>>x2>>y2;
		y1+=1;
		y2+=1;
		tot=0;
		if(y1>y2)
		{
			int dd=y1;
			y1=y2;
			y2=dd;
		}
		if(x1>x2)
		{
			int dd=x1;
			x1=x2;
			x2=dd;
		}
		for(int j=x1;j<=x2;j++)
		{    
			head=j*m+y1;
			tail=j*m+y2;
			if(tail>ans)tail=ans;
			//cout<<" T "<<tail<<endl;
		   if(head>tail)break;
			tot+=tail-head+1;
			}
		 //cout<<i<<" T  "<<tot<<endl;
		 ans-=tot;
		 //cout<<"A"<<" "<<ans<<endl;
	} 
	 cout<<ans<<endl;
	 return 0;
}