#include <iostream>
#include <iomanip>
#include <limits>
using namespace std;
int main(){
	int K;
	cin >> K;
	int count = 0;
	int A[] = { 2,3,5,7,11,13 };
	int B[] = { 4,6,8,9,10,12 };
	for (int i = 0; i < 6; i++) {
		for (int j = 0; j < 6; j++) {
			if ((A[i] * B[j]) == K)count++;
		}
	}
	double AVG = (double)count / 36.0;
	cout << fixed << setprecision(13) << AVG << endl;
	return 0;
}