// No.211 素数サイコロと合成数サイコロ (1)
// https://yukicoder.me/problems/no/211
//

#include <iostream>
#include <iomanip>
#include <vector>
using namespace std;

double solve(int K);


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

    double ans = solve(K);
    cout << setprecision(16) << fixed << ans << endl;
}

double solve(int K) {
    vector<int> dice1 {2, 3, 5, 7, 11, 13};
    vector<int> dice2 {4, 6, 8, 9, 10, 12};

    vector<int> products;
    for (auto i = 0; i < dice1.size(); i++) {
        for (auto j = 0; j < dice2.size(); j++) {
            products.push_back(dice1[i] * dice2[j]);
        }
    }

    int hit = 0;
    for (auto p: products) {
        if (p == K)
            hit++;
    }
    return static_cast<double>(hit) / products.size();
}