Rectangles Counting

Given N separate integer points on the Cartesian plane satisfying: there is no any three of them sharing a same X-coordinate. Your task is to count the number of rectangles (whose edges parrallel to the axes) created from any four of given points. Input There are several test cases (ten at most), each formed as follows: - The first line contains a positive integer N (N ≤ 105). - N lines follow