#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<cctype>
#include<cstdlib>
#include<algorithm>
#include<bitset>
#include<vector>
#include<list>
#include<deque>
#include<queue>
#include<map>
#include<set>
#include<stack>
#include<cmath>
#include<sstream>
#include<fstream>
#include<iomanip>
#include<ctime>
#include<complex>
#include<functional>
#include<climits>
#include<cassert>
#include<iterator>
#include<unordered_map>
#include<unordered_set>
using namespace std;
int a[] = { 2, 3, 5, 7, 11, 13 };
int b[] = { 4, 6, 8, 9, 10, 12 };
int main(){
	int countt = 0;
	int k;
	cin >> k;
	for (int i = 0; i < 6; i++){
		for (int j = 0; j < 6; j++){
			if (a[i] * b[j] == k){
				countt++;
			}
		}
	}
	double a = countt;
	double b = 6 * 6;
	a /= b;
	printf("%.16f\n", a);
	return 0;
}