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Taro and Hanako are playing Bunny Puzzle. There are several bunnies standing on a line. You are given a int bunnies, where each element is the initial position of a single bunny.
They must perform the following routine exactly once:
The jump is not allowed if another bunny is already at point 2*b-a.
The jump is also not allowed if A jumps over more than one bunny.
Return the number of different ways in which Taro and Hanako can choose the pair of bunnies A and B. "A jumps over B" and "B jumps over A" are considered to be different.
|-||bunnies will contain between 2 and 50 elements, inclusive.|
|-||Each element of bunnies will be between -10^6 and 10^6, inclusive.|
|-||bunnies will be sorted in strictly ascending order.|