#include <iostream>
#include <cstdio>
using namespace std;
int main(){
	freopen("deleteit.in","r",stdin);
	freopen("deleteit.out","w",stdout);
	int n,m;
	int ans=0;
	int q;
	scanf("%d %d %d",&n,&m,&q);
	int nnow=n,mnow=m;
	int X1,X2,Y1,Y2;
	int numnow=n*m;
	for(int i=1;i<=q;i++){
		scanf("%d %d %d %d",&X1,&Y1,&X2,&Y2);
		X1++,Y1++,X2++,Y2++;
		if(X1>nnow)
			continue;
		if(X1==nnow&&Y1>mnow)
			continue;
		X2=min(X2,nnow);
		int num=(X2-X1+1)*(Y2-Y1+1);
		if(X2==nnow&&Y2>mnow)
			num-=Y2-max(Y1,mnow+1)+1;
		ans+=num;
		numnow-=num;
		nnow=numnow/m+1;
		mnow=numnow%m;
		if(mnow==0)
			mnow=m;
	}
	printf("%d\n",numnow);
return 0;
}