
ZOJ Problem Set  3272
Description The city of M is a famous shopping city and its openair shopping malls are extremely attractive. During the tourist seasons, thousands of people crowded into these shopping malls and enjoy the varydifferent shopping. Unfortunately, the climate has changed little by little and now rainy days seriously affected the operation of openair shopping malls  it's obvious that nobody will have a good mood when shopping in the rain. In order to change this situation, the manager of these openair shopping malls would like to build a giant umbrella to solve this problem. These shopping malls can be considered as different circles. It is guaranteed that these circles will not intersect with each other and no circles will be contained in another one. The giant umbrella is also a circle. Due to some technical reasons, the center of the umbrella must coincide with the center of a shopping mall. Furthermore, a fine survey shows that for any mall, covering half of its area is enough for people to seek shelter from the rain, so the task is to decide the minimum radius of the giant umbrella so that for every shopping mall, the umbrella can cover at least half area of the mall. Input The input consists of multiple test cases. Output For each test case, output one line contains a real number rounded to 4 decimal places, representing the minimum radius of the giant umbrella that meets the demands. Sample Input 1 2 0 0 1 2 0 1 Sample Output 2.0822 Source: Asia 2009, Ningbo (Mainland China) 