只要努力飞翔，即使再弱小的蝴蝶也可以飞的很高
1580 - [Usaco2009 Hol]Cattle Bruisers 杀手游戏
输入
第1行输入N，R，BX，BY, BVX，BVY，之后N行每行输入四个整数Xi，Yi，VXi，VYi．
输出
一个整数，表示在逃脱过程中，某一个时刻最多有这个数理的杀手可以射杀贝茜．
样例
输入
3 1 0 0 0 2 0 -3 0 4 1 2 -1 1 1 -2 2 -1
输出
2 OUTPUT DETAILS: At time 1.5, Bessie is at point (0, 3), and the three bruisers are at points (0, 3), (-0.5, 3.5), and (4, -3.5). The first two cattle bruisers are within 1 unit of Bessie, while the third will never be within 1 unit of Bessie, so 2 is the most achievable.