import java.util.*;
import java.lang.*;
import java.io.*;
 
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		Scanner  in = new Scanner(System.in);
		int n, a=1, as=a, b=1;
		double sum=0.0, u=2.0;
		n = in.nextInt();
		for(int i=1, k=2; i<=n; i++, k++)
      	{
      		a=3*b+2*a;
      		b=2*as+b;
      		u*=(2.0/k);
      		sum+=u*(1.0/(1+a*a+b*b));
      		as=a;
      	}
       System.out.printf(Locale.US, "%.8f", sum); 
	}
}

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

NA==

4