1. 

/**
* FWP: Ausgewaehlte Probleme aus dem ACM (SS10)
*
* Problem: 11780 - Miles 2 Km
* Method: number theory
* Accepted: 0.288
* @author Evgeni Pavlidis
*
*/


import java.io.*;
import java.util.*;

class Main {

public static void main(String...args) throws Exception
{
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

int m;
while( (m = Integer.parseInt(reader.readLine())) != 0)
System.out.printf("%.2f\n", Math.abs((m*1.6) - Math.round(m*1.6)) );
}
}