/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		double x;
		System.out.printf("\n Ответ " );
		x=0;
		int n;
		Scanner in = new Scanner(System.in);
		n = in.nextInt();
		for(double i = 1; i <= n ; i++) 
		{
			x += 1/ ((2 * i)*(2 * i)) ;
		}
		System.out.printf("%.6f ",x);
	}
}

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

MTI4

128