#include<cstdio>
#include<algorithm>
#include<cmath>
using namespace std;
int num;
int n,m,q,x,y;
void Del(int x1,int y1,int x2,int y2){
//	x1=n-x1; x2=n-x2;
	int cnt=0;
	if (x<x1) return;
	if (x>x2){
		num-=(x2-x1+1)*(y2-y1+1);
		return;
	}
	x2=x;
	num-=(x2-x1+1)*(y2-y1+1);
	if (y<y1) {
		num+=y2-y1+1;
		return;
	}
	if (y>y2){
		return;
	}
	y1=y;
	num+=y2-y1;
}
void init(){
	x=num/m;
	if (num%m) x++;
	y=num%m;
	if (y==0) y=m;
}
void read(){
	scanf("%d%d%d",&n,&m,&q);
	num=n*m;
	x=n; y=m;
	int x1,y1,x2,y2;
	for (int i=1;i<=q;i++){
//		printf("%d\n",num);
		scanf("%d%d%d%d",&x1,&y1,&x2,&y2);
//		if (x1>=x2||y1>=y2) printf("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\n");
		Del(min(x1,x2)+1,min(y1,y2)+1,max(x1,x2)+1,max(y1,y2)+1);
		init();
	}
}
int main(){
	freopen("deleteit.in","r",stdin);
	freopen("deleteit.out","w",stdout); 
	read();
	printf("%d",num);
	return 0;
}