Mr.Cai is a peasant who owns some field,but due to his neglect,he earned little this year.Now autumn gradually away

from us,it is time to hand in taxs again,there are many exorbitant taxes and levies.After knowing Mr.Cai's poor condition ,

the landlord named "Zhou Ba Pi" said:"It's fine,just give me your field as hypothecate,since you must work on it to earn

money for me ,I won't take them all,I'll set a rule to show how will I take apart these field".

The rule is described as follow:give you a rectangle,means Mr.Cai's field,then give you another rectangle,if this two rectangles overlaped,Zhou will take this part away,so your task is to calculate the area of overlaped part.To make it easier,we confirm that every side is vertical or horizontal.

There are multiple test cases.Every case include 8 real numbers,each with two decimal point,a1,b1,a2,b2,a3,b3,a4 b4,first rectangle is (a1,b1) - (a2,b2),another is(a3,b3) - (a4,b4).
Look at Sample input,it's explain is like the picture shown above.

Each case output the area of overlaped part in a single line,and keep two decimal point too.