#include <iostream>
#include <iomanip>
#include <cstdlib>

using namespace std;

struct node
{
    double a, b, c, d;
    node(){}
    void add(double a, double b, double c, double d){ this->a = a; this->b = b; this->c = c; this->d = d; }
    void change(void)
    {     // 使得矩阵形式一样
        if (a > c) swap(a, c);
        if (b > d) swap(b, d);
        return;
    }
}matrix_1, matrix_2;

double min(double a, double b)
{
    return a<b ? a : b;
}
double max(double a, double b)
{
    return a>b ? a : b;
}
double calc()
{
    double x = min(matrix_1.c, matrix_2.c) - max(matrix_1.a, matrix_2.a);
    double y = min(matrix_1.d, matrix_2.d) - max(matrix_1.b, matrix_2.b);
    if (x < 0.00001 || y < 0.00001)
    {
        return 0.0;
    }
    else
    {
        return x * y;
    }
}

int main()
{
    double a, b, c, d;
    while (cin >> a >> b >> c >> d)
    {
        matrix_1.add(a, b, c, d);
        cin >> a >> b >> c >> d;
        matrix_2.add(a, b, c, d);
        matrix_1.change();
        matrix_2.change();
        cout << fixed << setprecision(2) << calc() << endl;
    }
    return 0;
}