import java.util.Scanner;

public class Main{
	public static void main(String[] args){
		Scanner sc=new Scanner(System.in);
		int[] a={2,3,5,7,11,13}; int[] b={4,6,8,9,10,12};
		while(sc.hasNext()){
			double[] dp=new double[201];
			for(int i=0;i<6;i++) for(int j=0;j<6;j++) dp[a[i]*b[j]]++;
			for(int i=0;i<201;i++) dp[i]/=36.0;
			int k=sc.nextInt();
			System.out.println(dp[k]);
		}
	}
}