#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000

int main(){
	
	int K;
	cin>>K;
	
	vector<double> dp(K+1,0.0);
	dp.back() = 0.0;
	
	for(int i=K-1;i>=0;i--){
		rep(j,6){
			int nxt = min(i+j+1,K);
			dp[i] += dp[nxt] / 6.0;
		}
		dp[i] += 1.0;
	}
	
	cout<<fixed<<setprecision(10)<<dp[0]<<endl;
	
	return 0;
}