Problem:
Score : 100 points

Problem Statement

Given is an integer N.

Takahashi chooses an integer a from the positive integers not greater than N with equal probability.

Find the probability that a is odd.

Constraints

1 \leq N \leq 100

Input

Input is given from Standard Input in the following format:

N

Output

Print the probability that a is odd.
Your output will be considered correct when its absolute or relative error from the judge's output is at most 10^{-6}.

Sample Input 1

4

Sample Output 1

0.5000000000

There are four positive integers not greater than 4: 1, 2, 3, and 4. Among them, we have two odd numbers: 1 and 3. Thus, the answer is \frac{2}{4} = 0.5.

Sample Input 2

5

Sample Output 2

0.6000000000

Sample Input 3

1

Sample Output 3

1.0000000000

Solution in Scala (2.11.7) (judge verdict: Runtime Error)

import java.io.{BufferedReader, InputStreamReader}

object Main {
  def main(args: Array[String]): Unit = {
    val in = new BufferedReader(new InputStreamReader(System.in))
    val Array(a, b) = in.readLine().split("\\s+").map(_.toInt)

    System.out.println((prime(a).toSet & prime(b).toSet).size)
  }


  def prime(n: Int): List[Int] = {
    def _prime(n: Int, ps: List[Int]): List[Int] = {
      (2 to n).find(n % _ == 0) match {
        case Some(p) => _prime(n / p, p :: ps)
        case None => n :: ps
      }
    }

    _prime(n, Nil)
  }
}