7869: BZOJ3869：Hero’s assistant

There is an old country and the king fell in love with a devil. The devil always asks the king to do some crazy things. Although the king used to be wise and beloved by his people. Now he is just like a boy in love and can’t refuse any request from the devil. Also, this devil is looking like a very cute Loli. Y*wan find that the only way to save this country is to kill every loli. Y*wan is fine about that because he doesn't like loli. But the princess's knight's member just thinks he is insane. So they compete in an algorithm contest. In this contest, Y*wan suck at this problem, if y*wan can't win, the mankind will become extinct, so it's your turn to help y*wan solve this problem. There are n points in the plane, you pick a random point in [0,X] x [0,Y], after that you output the second nearest squared distance from this point to those n points. What is the expectation of your output?

输入格式

The first line contains an integer T, denoting the number of the test cases. For each test case, the first line contains 3 integers n,X,Y. The next n lines, each contains 2 integers x, y, denote that there is a point x,y. T<=5,2<=n<=100. 0<=X,Y<=100 , -200<=x,y<=200

输出格式

For each test case, output the answer in one line. This problem is special judged. The relative error less than 1e-6 will be accepted.

样例输入

1
2 10 10
0 0
10 10

样例输出

100.0000000000

提示

请不要提交，期待SPJ

题目来源

By WJMZBMR