#include <bits/stdc++.h>

using namespace std;

typedef pair<int,int> P;
typedef pair<int,pair<int,int>> PP;
typedef long long ll;

const double EPS = 1e-8;
const int INF = 1e9;
const int MOD = 1e9+7;

int dy[] = {0,1,0,-1};
int dx[] = {1,0,-1,0};

std::mt19937 mt((int)time(0));
int sim(const int& k){
	int sum = 0,cnt = 0;
	while(sum != k){
		sum += mt()%6+1;
		cnt++;
		if(sum > k)sum = 0;
	}
	return cnt;
}

int main(void) {
	int k;
	cin >> k;
	
	const int N = 1e6;
	int count = 0;

	for(int i=0;i<N;i++){
		count += sim(k);
	}

	cout << fixed << setprecision(10) << (double)count/N << endl;
	return 0;
}