import java.util.Scanner;
// 1:无需package
// 2: 类名必须Main, 不可修改
public class Main {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
int x1 = scan.nextInt();
int y1 = scan.nextInt();
int x2 = scan.nextInt();
int y2 = scan.nextInt();
int x3 = scan.nextInt();
int y3 = scan.nextInt();
int x4 = scan.nextInt();
int y4 = scan.nextInt();
//在此输入您的代码...
//先计算总面积
long sum = 0;
sum = (long)(y2 - y1) * (x2 - x1) + (long) (y4 - y3) * (x4 - x3);
//计算是否有重叠区域
if(x3 >= x2 || y3 >= y2 || x1 >= x4 || y1 >= y4) {
System.out.println(sum);
}else {
int xl = Math.max(x1, x3);
int yl = Math.max(y1, y3);
int xr = Math.min(x2, x4);
int yr = Math.min(y2, y4);
long sub = (long) ((yr - yl) * (xr - xl));
System.out.println(sum - sub);
}
scan.close();
}
}