#include <iostream>
#include <cstdio>
using namespace std;
int n,m,Q,ans,h,l;
int main()
{
//	freopen("abcd.in","r",stdin);
	freopen("deleteit.in","r",stdin);
	freopen("deleteit.out","w",stdout);
	scanf("%d%d%d",&n,&m,&Q);
	ans=n*m;
	h=n;l=0;
	int x1,x2,y1,y2;
	while(Q--)
	{
		scanf("%d%d%d%d",&x1,&y1,&x2,&y2);
		x1++;y1++;x2++;y2++;
		int sd=y2-y1+1;
		sd=sd*( min(x2,h)-x1+1 );
	//	cout<<'*'<<h<<' '<<x1<<' '<<sd<<" ";
		if(l>=y1)
			sd+=min( l,y2 )-y1+1;
		ans-=sd;
		h=ans/m;
		l=ans%m;
	//	cout<<"SB"<<sd<<' '<<h<<' '<<l<<endl;
		
	}
	printf("%d\n",ans);
	return 0;
}