시간 제한메모리 제한제출정답맞힌 사람정답 비율
1 초 128 MB6021689829.697%

문제

2차원 평면 위에 점 N개가 있다.

세 점을 골랐을 때, 직각 삼각형을 이루는 것의 쌍의 수를 구하는 프로그램을 작성하시오. 직각 삼각형이란 한 각이 90도인 삼각형이다.

입력

첫째 줄에 점의 수 N이 주어진다. (3 ≤ N ≤ 1500)

다음 N개 줄에는 점의 x좌표와 y좌표가 공백으로 구분되어진 상태로 주어진다. 좌표는 -109와 109 사이이다. 두 점이 같은 좌표를 갖는 경우는 없다.

출력

첫째 줄에 직각 삼각형의 개수를 출력한다.

예제 입력 1

3
4 2
2 1
1 3

예제 출력 1

1

예제 입력 2

4
5 0
2 6
8 6
5 7

예제 출력 2

0

예제 입력 3

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

예제 출력 3

7
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출처

Contest > Croatian Open Competition in Informatics > COCI 2007/2008 > Contest #2 6번