Codeforces Round 755 (Div. 1, based on Technocup 2022 Elimination Round 2)
E
Eligible Segments
Codeforces
未评级
原题
← DF →
翻译中…

You are given $n$ distinct points $p_1, p_2, \ldots, p_n$ on the plane and a positive integer $R$.

翻译中…

Find the number of pairs of indices $(i, j)$ such that $1 \le i \lt j \le n$, and for every possible $k$ ($1 \le k \le n$) the distance from the point $p_k$ to the segment between points $p_i$ and $p_j$ is at most $R$.

翻译中…

Input

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The first line contains two integers $n$, $R$ ($1 \le n \le 3000$, $1 \le R \le 10^5$) — the number of points and the maximum distance between a point and a segment.

翻译中…

Each of the next $n$ lines contains two integers $x_i$, $y_i$ ($-10^5 \le x_i, y_i \le 10^5$) that define the $i$-th point $p_i=(x_i, y_i)$. All points are distinct.

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It is guaranteed that the answer does not change if the parameter $R$ is changed by at most $10^{-2}$.

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Output

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Print the number of suitable pairs $(i, j)$.

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Note

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In the first example, the only pair of points $(-3, 0)$, $(3, 0)$ is suitable. The distance to the segment between these points from the points $(0, 1)$ and $(0, -1)$ is equal to $1$, which is less than $R=2$.

翻译中…

In the second example, all possible pairs of points are eligible.

翻译中…

样例

Input #1
4 2
0 1
0 -1
3 0
-3 0
Output #1
1
InputCopy OutputCopy
Input #2
3 3
1 -1
-1 -1
0 1
Output #2
3
InputCopy OutputCopy
题目信息
题号
1588E
时间限制
3 s
内存限制
256 MB

题面与样例版权归 Codeforces 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。