AtCoder Beginner Contest 187
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Problem Statement
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On the $xy$-plane, We have $N$ points numbered $1$ to $N$. Point $i$ is at $(x_i, y_i)$, and the $x$-coordinates of the $N$ points are pairwise different.
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Find the number of pairs of integers $(i, j)\ (i < j)$ that satisfy the following condition:
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- The line passing through Point
$i$and Point$j$has a slope between$-1$and$1$(inclusive).
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Constraints
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- All values in input are integers.
$1 \le N \le 10^3$$|x_i|, |y_i| \le 10^3$$x_i \neq x_j$for$i \neq j$.
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Input
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Input is given from Standard Input in the following format:
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N
x_1 y_1
\vdots
x_N y_N翻译中…
Output
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Print the answer.
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样例
Input #1
3
0 0
1 2
2 1
Output #1
2
The slopes of the lines passing through $(0, 0)$ and $(1, 2)$, passing through $(0, 0)$ and $(2, 1)$, and passing through $(1, 2)$ and $(2, 1)$ are $2$, $\frac{1}{2}$, and $-1$, respectively.
Input #2
1
-691 273
Output #2
0
Input #3
10
-31 -35
8 -36
22 64
5 73
-14 8
18 -58
-41 -85
1 -88
-21 -85
-11 82
Output #3
11
题目信息
题面与样例版权归 AtCoder 及出题人所有；中文翻译由 AI 生成（CI 管线），如有出入请以原文为准。