# 11097: 【原1097】Enclose

### 题目描述

author: Guangda Huzhang 原OJ链接：https://acm.sjtu.edu.cn/OnlineJudge-old/problem/1097

## Description

There are n circles in a plane with equal radius. Now we wanna draw a shortest enclosed curve, and every circles lie in this curve. You have to write a program to calculate the length of this curve.

## Input Format

The input contains multiple testcases.

For each case, the first line contains two integer $$n$$ and $$r$$ $$(1\leq n\leq 10000)$$ denoting the number of circles and the radius of them. After that there are $$n$$ lines, each line contains two integers denoting the coordinate of each circle.The absolute value of then would not be greater then 10000, and the radius is no large than 10000.

## Output Format

For each case output one real number (round to 0.01) which is the length of that curve.

## Sample Input

2 1
-1 0
1 0
5 1
1 0
0 1
-1 0
0 -1
0 0


## Sample Output

10.28
11.94


## Case Limits

Time limit: 500 msec

Memory limit: 64 MB

## Oops! 本题目还没有解答！

OJ翻了一新，但本解答集还大多用的是2017-2019级，甚至更早的同学们贡献的答案。