import java.util.Scanner;

 public class Main {

     public static void main(String[] args) {

         Scanner sc = new Scanner(System.in);

         double[] x = new double[4];

         double[] y = new double[4];

         double[] z = new double[4];

         for(int i=0;i<4;i++){

             x[i] = sc.nextDouble();

             y[i] = sc.nextDouble();

         }

         z[0] = Math.max(Math.min(x[0], x[1]),Math.min(x[2], x[3])); //x1

         z[1] = Math.min(Math.max(x[0], x[1]),Math.max(x[2], x[3])); //x2

         z[2] = Math.max(Math.min(y[0], y[1]),Math.min(y[2], y[3])); //y1

         z[3] = Math.min(Math.max(y[0], y[1]),Math.max(y[2], y[3])); //y2

         if(z[0]<z[1]&&z[2]<z[3])

             System.out.printf("%.2f\n",(z[1]-z[0])*(z[3]-z[2]));

         else

             System.out.println("0.00");

     }

 }