
ZOJ Problem Set  1090
To calculate the circumference of a circle seems to be an easy task  provided you know its diameter. But what if you don't?
You are given the cartesian coordinates of three noncollinear points in the plane. Input SpecificationThe input file will contain one or more test cases. Each test case consists of one line containing six real numbers x_{1},y_{1}, x_{2},y_{2},x_{3},y_{3}, representing the coordinates of the three points. The diameter of the circle determined by the three points will never exceed a million. Input is terminated by end of file.Output SpecificationFor each test case, print one line containing one real number telling the circumference of the circle determined by the three points. The circumference is to be printed accurately rounded to two decimals. The value of pi is approximately 3.141592653589793.Sample Input0.0 0.5 0.5 0.0 0.0 0.5 0.0 0.0 0.0 1.0 1.0 1.0 5.0 5.0 5.0 7.0 4.0 6.0 0.0 0.0 1.0 7.0 7.0 7.0 50.0 50.0 50.0 70.0 40.0 60.0 0.0 0.0 10.0 0.0 20.0 1.0 0.0 500000.0 500000.0 0.0 0.0 500000.0 Sample Output3.14 4.44 6.28 31.42 62.83 632.24 3141592.65 Source: University of Ulm Local Contest 1996 