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NN and the Optical Illusion（数学）

NN is an experienced internet user and that means he spends a lot of

time on the social media. Once he found the following image on the

Net, which asked him to compare the sizes of inner circles:

It turned out that the circles are equal. NN was very surprised by

this fact, so he decided to create a similar picture himself.

He managed to calculate the number of outer circles n and the radius

of the inner circle r. NN thinks that, using this information, you can

exactly determine the radius of the outer circles R so that the inner

circle touches all of the outer ones externally and each pair of

neighboring outer circles also touches each other. While NN tried very

hard to guess the required radius, he didn’t manage to do that.

Help NN find the required radius for building the required picture.

Input

The first and the only line of the input file contains two numbers n

and r (3≤n≤100, 1≤r≤100) — the number of the outer circles and the

radius of the inner circle respectively.

Output

Output a single number R — the radius of the outer circle required for

building the required picture.

Your answer will be accepted if its relative or absolute error does

not exceed 10−6.

Formally, if your answer is a and the jury’s answer is b. Your answer

is accepted if and only when |a−b|max(1,|b|)≤10−6.

Examples Input

3 1

标题Output

6.4641016

标题Input

6 1

Output

这里是引用

1.0000000

Input

100 100

Output

3.2429391

代码如下（数学计算）：

#include 
   
    #include 
    
     #include
     
      #define pi 3.1415926535int main(){    double n,r;    scanf("%lf%lf",&n,&r);    double x=pi*(n-2)/n;    printf("%.7f\n",r*cos(x/2)/(1-cos(x/2)));    return 0;}
     
    
   

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