#include <iostream>
#include <vector>
#include <cstdio>
#include <sstream>
#include <map>
#include <string>
#include <algorithm>
#include <queue>
#include <cmath>
#include <set>
using namespace std;

int a[] = {2,3,5,7,11,13};
int b[] = {4,6,8,9,10,12};


int main(){
	int k;
	cin >> k;

	int x = 0;
	int y = 0;
	for(int i=0; i<6; i++){
		for(int j=0; j<6; j++){
			if(a[i]*b[j] == k) y++;
			x++;
		}
	}

	printf("%.18f\n", y/(double)x);
	return 0;
}