#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i = (a); i < (b); ++i)
#define REP(i,n) FOR(i,0,n)
#define SZ(n) (int)(n).size()
using namespace std;
typedef long long ll;
typedef vector<int> VI;

int main() {
	int so[6] = { 2,3,5,7,11,13 };
	int go[6] = { 4,6,8,9,10,12 };
	int k;
	cin >> k;
	int cnt = 0;
	REP(i, 6) {
		REP(j, 6) {
			if (k == so[i] * go[j]) {
				cnt++;
				break;
			}
		}
	}
	cout << setprecision(12) << fixed << cnt / 36.0 << endl;
	return 0;
}