import java.util.*

fun main(args: Array<String>) {
    val sc = java.util.Scanner(System.`in`)
    val n = sc.nextInt()

    val r = (1..n)
    val sum = r.asSequence().filter { it % 2 == 1 }.count()
    val len = r.count()
    println(sum.toDouble() / len.toDouble())
}

