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ZOJ Problem Set - 1597
Circular Area

Time Limit: 2 Seconds      Memory Limit: 65536 KB

Your task is to write a program, which, given two circles, calculates the area of their intersection with the accuracy of three digits after decimal point.


Input

In the single line of input file there are space-separated real numbers x1 y1 r1 x2 y2 r2. They represent center coordinates and radii of two circles.

Process to the end of input.


Output

The output file must contain single real number - the area.


Sample Input

20.0 30.0 15.0 40.0 30.0 30.0


Sample Output

608.366


Source: Northeastern Europe 2000, Far-Eastern Subregion
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