package yukicoder;

import java.util.Scanner;

public class N428
{
	public static void main(String[] args)
	{
		Scanner sc=new Scanner (System.in);
		String D = "0.1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798991";
		int[] s=new int[190+2];
		int N=sc.nextInt();
		for(int i=0+2;i<190+2;i++)
		{
			s[i]=N*Integer.parseInt(D.substring(i, i+1));
		}
		s[0]=0;s[1]=0;
		for(int i=189+2;i>=0+2;i--)
		{
			if(i>=3){s[i-3]+=s[i]/1000;}
			s[i-2]+=s[i]/100;
			s[i-1]+=(s[i]/10)%10;
			s[i]=s[i]%10;
		}

		if(s[1]>=10)
		{
			s[0]+=s[1]/10;s[1]=s[1]%10;
		}


		System.out.print(s[0]+""+s[1]+".");
		for(int i=2;i<192;i++)
		{
			System.out.print(s[i]);
		}

	}

}