作为一个生活散漫的人，小Z每天早上都要耗费很久从一堆五颜六色的袜子中找出一双来穿。终于有一天，小Z再也无法忍受这恼人的找袜子过程，于是他决定听天由命……
具体来说，小Z把这N只袜子从1到N编号，然后从编号L到R(L 尽管小Z并不在意两只袜子是不是完整的一双，甚至不在意两只袜子是否一左一右，他却很在意袜子的颜色，毕竟穿两只不同色的袜子会很尴尬。
你的任务便是告诉小Z，他有多大的概率抽到两只颜色相同的袜子。当然，小Z希望这个概率尽量高，所以他可能会询问多个(L,R)以方便自己选择。(As a loose person, little Z spend a lot of time in the morning to find a pair of clothes from a pile of colorful socks. Finally, one day, little Z could no longer bear this annoying process of finding socks, so he decided to listen to his fate.
Specifically, the little Z numbered the N socks from 1 to N, and then from the number L to the R (L although the small Z doesn't care whether the two socks are a complete pair or even if the two socks are left or right, he is very concerned with the color of the socks, after all, wearing two different colors will be embarrassing. "
Your task is to tell little Z how much he can draw two socks of the same color. Of course, small Z expects this probability to be as high as possible, so he may ask multiple L (R) to make her own choice.)