#include<algorithm>
using namespace std;
int z1,y1,s1,x1; 
struct c
{
	int z,y,s,x;
}a[99];
int main()
{
	cin>>a[1].z>>a[1].y>>a[1].s>>a[1].x;
	cin>>a[2].z>>a[2].y>>a[2].s>>a[2].x;
	if(a[1].z>a[2].z) z1=a[1].z;
	else z1=a[2].z;
	if(a[1].y<a[2].y) y1=a[1].y;
	else y1=a[2].y;
	if(a[1].s>a[2].s) s1=a[1].s;
	else s1=a[2].s;
	if(a[1].x<a[2].x) x1=a[1].x;
	else x1=a[2].x;
	if(z1<y1&&s1<x1)
	cout<<(y1-z1)*(x1-s1);
	else cout<<0;
	return 0;
 }