#include<iostream>
#include<cstdio>
#include<algorithm>
#include<string>

using namespace std;
int main() 
{
	double x1,y1,x2,y2;
	double x3,y3,x4,y4;
	double x5,y5,x6,y6;
	cin>>x1>>y1>>x2>>y2>>x3>>y3>>x4>>y4;
	
	x5 = min(max(x1,x2) , max(x3,x4));
	y5 = min(max(y1,y2) , max(y3,y4));
	
	x6 = max(min(x1,x2) , min(x3,x4));
	y6 = max(min(y1,y2) , min(y3,y4)); 
	
	if(x5>x6&&y5>y6)
		printf("%.2lf",(x5-x6)*(y5-y6));
	else
		printf("0.00");
	
	return 0;
}