在一个二维平面上给定N个点（4 <= N<=1000 ）Pi(xi,yi) ( Pi(xi,yi) ( |xi| <= 20000 ,|yi| <= 20000,不存在重复点 存在重复点 ), 请问在这些点中能形成多少个正方。 -Given a two-dimensional plane of N points (4 < = N < = 1000) Pi, (xi, yi) (Pi (xi, yi) (| xi | < = 20000, | yi | < = 20000 does not exist repeat duplicate points), does the square of the number of these points can be formed.