import java.io.*;
import java.text.DecimalFormat;
import java.util.*;
public class Main {
	public static void main(String[] args) {
		Scanner sc=new Scanner(new BufferedInputStream(System.in));
		while(sc.hasNextDouble()){
			double s=0;
			double res[]=new double[4];
			double res1[]=new double[4];
			double res2[]=new double[4];
			double point1[]=new double[4];
			double point2[]=new double[4];
			for(int i=0;i<point1.length;i++){
				point1[i]=sc.nextDouble();
			}
			for(int i=0;i<point2.length;i++){
				point2[i]=sc.nextDouble();
			}
			//  第一个矩形左上角的坐标
			res1[0]=Math.min(point1[0], point1[2]);//X1
			res1[1]=Math.max(point1[1], point1[3]);//Y1
			//第一个矩形右下角的坐标
			res1[2]=Math.max(point1[0], point1[2]);//x2
			res1[3]=Math.min(point1[1], point1[3]);//y2
			//  第二个矩形左上角的坐标
			res2[0]=Math.min(point2[0], point2[2]);//x1
			res2[1]=Math.max(point2[1], point2[3]);//y1
			// 第二个矩形右下角的坐标
			res2[2]=Math.max(point2[0], point2[2]);//x2
			res2[3]=Math.min(point2[1], point2[3]);//y2
			// 如果矩形重合和相离  s=0  
			if(res2[0]>=res1[2]||res2[2]<=res1[0]||res2[3]>=res1[1]||res2[1]<=res1[3]){
				s=0;
			}
			else{
				//否者矩形相交的 坐标
				res[0]=Math.max(res1[0], res2[0]);
				res[1]=Math.min(res1[1],res2[1]);
				res[2]=Math.min(res1[2],res2[2]);
				res[3]=Math.max(res1[3],res2[3]);
				s=(res[2]-res[0])*(res[1]-res[3]);
			}
			DecimalFormat fo=new DecimalFormat("0.00");
			System.out.println(fo.format(s));
		}
	}

}


//java/8358