#include <bits/stdc++.h>
#define rep(i,n) for(int i=(0);i<(n);i++)

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;

template<class T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a=b; return 1; } return 0; }

map<int, double> memo;

double rec(int x){
	if(x <= 0) return memo[x] = 0;
	if(memo.count(x) > 0) return memo[x];
	
	double ret = 1.0;
	rep(i, 6) ret += rec(x - (i + 1)) / 6.0;
	return memo[x] = ret;
}

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);

	int k;
	cin >> k;

	cout << fixed << setprecision(10);
	cout << rec(k) << endl;
}