import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int k = sc.nextInt();
		int x = 0, y = 0;
		int[] a = {2,3,5,7,11,13};
		int[] b = {4,6,8,9,10,12};
		for(int i = 0 ; i < a.length ; i++) {
			for(int j = 0 ; j < b.length ; j++) {
				x++;
				if(k == a[i] * b[j]) y++;
			}
		}
		System.out.printf("%.12f\n", 1.0 * y / x);
 	}
}