#include <iomanip>
#include <algorithm>
using namespace std;

int main()
{
    double x1,y1,x2,y2;
    // 读第一个矩形
    cin >> x1 >> y1 >> x2 >> y2;
    double r1_xmin = min(x1,x2);
    double r1_xmax = max(x1,x2);
    double r1_ymin = min(y1,y2);
    double r1_ymax = max(y1,y2);

    // 读第二个矩形
    cin >> x1 >> y1 >> x2 >> y2;
    double r2_xmin = min(x1,x2);
    double r2_xmax = max(x1,x2);
    double r2_ymin = min(y1,y2);
    double r2_ymax = max(y1,y2);

    // 求交集边界
    double ix1 = max(r1_xmin, r2_xmin);
    double iy1 = max(r1_ymin, r2_ymin);
    double ix2 = min(r1_xmax, r2_xmax);
    double iy2 = min(r1_ymax, r2_ymax);

    double area = 0.0;
    if(ix1 < ix2 && iy1 < iy2)
    {
        area = (ix2 - ix1) * (iy2 - iy1);
    }
    // 保留两位小数输出
    cout << fixed << setprecision(2) << area << endl;
    return 0;
}