#include<cstdio>
#include<algorithm>
namespace IO{
	char buf[1<<15],*fs,*ft;
	inline char gc(){return (fs==ft&&(ft=(fs=buf)+fread(buf,1,1<<15,stdin),fs==ft))?0:*fs++;}
	inline int qr(){
		int x=0,ch=gc();
		while(ch<'0'||ch>'9'){ch=gc();}
		while(ch>='0'&&ch<='9'){x=(x<<1)+(x<<3)+ch-'0';ch=gc();}
		return x;}
}using namespace IO;
using namespace std;
/***********************************************************************************************/
int lrj(){
	freopen ("deleteit.in","r",stdin);
	freopen ("deleteit.out","w",stdout);
	int n,m,q,now,x1,y1,x2,y2,i,h,l;
	n=qr();m=qr();q=qr();
	now=n*m;
	for(i=0;i<q;i++){
		x1=qr();y1=qr();x2=qr();y2=qr();
		l=now%m;
		h=(now-l)/m;
		if(l!=0){h++;}
		if(l==0){l=m;}
		x1++;x2++;y1++;y2++;
		if(h<x1||(x1==h&&y1>l)){continue;}
		if(h<x2){
			x2=h;}
		if(x2==h&&y2>l){
			now=now-(x2-x1+1)*(y2-y1+1)+y2-max(y1,l+1)+1;}
		else{
			now=now-(x2-x1+1)*(y2-y1+1);}
	}
	printf("%d",now);
	return 0;
}
int c=lrj();
int main(){;}