import java.util.*;


public class Main {
    public static void main(String[] args){

        Scanner s = new Scanner(System.in);
        double n = s.nextInt();

        String ans;
        if(n%2 == 0) {
          ans = "0.5000000000";
        } else {
          ans = String.format("%.10f", (n+1)/(2*n));
        }

        System.out.println(ans);
    }
}
/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