#include <iostream>
#include <numeric>
#include <algorithm>
#include <string>
#include <vector>
#include <cmath>
#include <queue>

#define rep(i, a) FOR(i, 0, a)
#define FOR(i, a, b) for(int i = a; i < b; ++i)

int k;
double ans[201];
int a[6] = { 2, 3, 5, 7, 11, 13 }, b[6] = { 4, 6, 8, 9, 10, 12 };

int main(){
	rep(i, 6)rep(j, 6)ans[a[i] * b[j]] += (1 / 36.0);
	std::cin >> k;
	printf("%.13lf\n", ans[k]);
	return 0;
}