COCI '07 Contest 2 #6 Pravokutni

View as PDF

Submit solution


Points: 10
Time limit: 0.4s
Memory limit: 32M

Problem types

N points are placed in the coordinate plane.

Write a program which calculates in how many ways a right triangle can be formed by three of the given points. A right triangle is one in which one of the angles is 90 degrees.

Input Specification

The first line of input contains an integer N (3N1500), the number of points.

Each of the following N lines contains the coordinates of one point, two integers separated by a space. The coordinates will be between 109 and 109.

No two points will be located at the same coordinates.

Output Specification

Output the number of right triangles.

Sample Input 1

Copy
3
4 2
2 1
1 3

Sample Output 1

Copy
1

Sample Input 2

Copy
4
5 0
2 6
8 6
5 7

Sample Output 2

Copy
0

Sample Input 3

Copy
5
-1 1
-1 0
0 0
1 0
1 1

Sample Output 3

Copy
7

Comments

There are no comments at the moment.