//调了半天，发现这道题的判断没有想象中的复杂……代码缩减一半。
//2016.11.16
#include<cstdio>
using namespace std;
int n,m,t,s,p,q;
void del(){
	int x1,y1,x2,y2;
	scanf("%d%d%d%d",&x1,&y1,&x2,&y2);
	int i,j;
	for(i=x1;i<=x2;i++){
		for(j=y1;j<=y2;j++){
			if(i<p-1){
				s--;
				continue;
			}
			if(i==p-1){
				if(j<q){
					s--;
					continue;
				}
			}
		}
	}
	p=s/m+1;
	q=s%n+1;
}
int main(){
	freopen("deleteit.in","r",stdin);
	freopen("deleteit.out","w",stdout);
	scanf("%d%d%d",&n,&m,&t);
	s=n*m;
	p=n,q=m;
	int i;
	for(i=0;i<t;i++)del();
	printf("%d",s);
	return 0;
}