/************************************************
Grundlegende Algorithmen mit Java,
http://algorithmen-und-problemloesungen.de/
Copyright @2007-2009 by Doina Logofatu
************************************************/

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

public class P08Oktoberfest4 {
  private static final String FileInputName = "oktoberfest.in";
  private static final String FileOutputName = "oktoberfest.out";
  private static final int NMAX = 501;

  public static void main(String[] args) throws IOException {
    Scanner scanner = null;
    PrintStream out = null;
    try {
      float t[] = new float[NMAX];
      t[0] = 1f;
      for (int i = 1; i < NMAX; i++) {
        t[i] = (2f * i - 1.0f) / (2f * i) * t[i - 1];
      }
      scanner = new Scanner(new File(FileInputName));
      out = new PrintStream(new File(FileOutputName));
      while (scanner.hasNextInt()) {
        int n = scanner.nextInt();
        out.printf(Locale.ENGLISH, "%3d: %.4f%n", n, 1 - t[n - 1]);
      }
    } finally {
      if (scanner != null) {
        scanner.close();
      }
      if (out != null) {
        out.close();
      }
    }
  }
}