#include <stdio.h>
#include <iostream>
using namespace std;

const int P[] = {2,3,5,7,11,13};
const int C[] = {4,6,8,9,10,12};
int K;

double solve()
{
    int cnt = 0;
    for (int i = 0; i < 6; i++) {
        for (int ii = 0; ii < 6; ii++) {
            if (K == (P[i] * C[ii])) {
                cnt++;
            }
        }
    }
    return (double)cnt / (6 * 6);
}

int main()
{
    cin >> K;
    printf("%.19f\n", solve());
}