시간 제한메모리 제한제출정답맞힌 사람정답 비율
1 초 1024 MB42816715047.619%

문제

창하는 재작년 미술 수업 최종 프로젝트로 다음과 같은 그림을 그린 덕분에 과목우수상을 받았다.

  1. 비어있는 2차원 좌표평면을 준비한다.
  2. $N$개의 점 $(X_1, Y_1), (X_2, Y_2), \cdots, (X_N, Y_N)$을 정한다. 단, $Y_i > 0$이다.
  3. $x$축을 나타내는 직선을 그린다.
  4. $i = 1, 2, \cdots, N$에 대해 점 $(X_i, Y_i)$을 지나고, 기울기가 각각 $1$과 $-1$인 두 개의 직선을 그린다. 단, $x$축 아래의 부분은 그리지 않는다.

아래는 창하의 그림의 예시를 나타낸 것이다.

과목우수상의 비결은 그림에 등장하는 교점의 아름다운 조화라고 생각한 에릭은 창하의 그림에 등장하는 서로 다른 교점의 개수를 구해보고자 한다. 이때 완전히 겹치는 직선들은 하나의 직선으로 취급한다.

입력

첫 번째 줄에 정수 $N$이 주어진다.

다음 $N$개의 줄 중 $i$번째 줄에 두 개의 정수 $X_i$, $Y_i$가 공백으로 구분되어 주어진다.

출력

창하의 그림에 등장하는 서로 다른 교점의 개수를 출력한다.

제한

  • $1 \le N \le 2 \times 10^5$
  • $-10^9 \le X_i \le 10^9$
  • $1 \le Y_i \le 10^9$

서브태스크

번호배점제한
110

$X_1 = X_2 = \cdots = X_N$

225

$N \le 1000$

365

추가 제약 조건 없음

예제 입력 1

3
4 3
6 1
8 1

예제 출력 1

9
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채점 및 기타 정보

  • 예제는 채점하지 않는다.