import java.util.Scanner;

class Main {
  public static void main(String args[]) {
    Scanner sc = new Scanner(System.in);

    int N = sc.nextInt();

    int remainder = N % 2;
    int quotient = N / 2;

    if (remainder == 0) {
      System.out.println("0.5000000000");
    } else {
      double probability = (quotient + 1.0) / N;
      System.out.println(probability);
    }
  }
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz