#include <bits/stdc++.h>
#include <iostream>
#include <vector>
#include <queue>
#include <string>
#include <cstring>
#include <sstream>
#include <set>
#include <map>
#include <algorithm>
#include <cstdio>
#include <cstdlib>

#define rep(i,n) for(int i=0;i<(int)(n);++i)
#define F first
#define S second
#define SZ(a) (int)((a).size())
#define sz(a) SZ(a)
#define pb(a) push_back(a)
#define mp(a,b) make_pair(a,b)
#define ALL(a) (a).begin(),(a).end()
using namespace std;

typedef long long ll;
typedef pair<ll,ll> PI;
typedef unsigned long long ull;

#define PR(...) do{cerr << "line : " << __LINE__ << endl; pr(#__VA_ARGS__, __VA_ARGS__);}while(0);
template<class T>
void pr(const string& name, T t){
  cerr << name << ": " << t << endl;
}

template<typename T, typename ... Types>
void pr(const string& names, T t, Types ... rest) {
  auto comma_pos = names.find(',');
  cerr << names.substr(0, comma_pos) << ": " << t << ", ";
  
  auto next_name_pos = names.find_first_not_of(" \t\n", comma_pos + 1);
  pr(string(names, next_name_pos), rest ...);
}

template<class T,class U> ostream& operator<< (ostream& o, const pair<T,U>& v){return o << "(" << v.F << ", " << v.S << ")";}
template<class T> ostream& operator<< (ostream& o, const vector<T>& v){o << "{";rep(i,SZ(v)) o << (i?", ":"") << v[i];return o << "}";}


#define endl '\n'
int k;
double memo[201][110];
bool vis[201][110];
double rec(int cur,int t){
  if(t > 100) return 0;
  if(cur == k) return 0;
  if(cur > k){
    cur = 0;
    ++t;
  }
  if(vis[cur][t]) return memo[cur][t];
  vis[cur][t] = 1;
  double& ret = memo[cur][t];
  for(int i = 1; i <= 6; ++i)
    ret += (rec(cur+i,t)+1)/6;
  return ret;
}

int main(int argc, char *argv[])
{
  cin >> k;
  printf("%.8f\n", rec(0,0));
  return 0;
}