#include <iostream>
#include <cstdio>
#include <fstream>
#include <algorithm>
#include <string>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <vector>
#include <limits.h>
#include <math.h>
#include <functional>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <float.h>
#include <random>

#define repeat(i,n) for (long long i = 0; (i) < (n); ++ (i))
#define debug(x) cerr << #x << ": " << x << '\n'
#define debugArray(x,n) for(long long hoge = 0; (hoge) < (n); ++ (hoge)) cerr << #x << "[" << hoge << "]: " << x[hoge] << '\n'
#define debugArrayP(x,n) for(long long hoge = 0; (hoge) < (n); ++ (hoge)) cerr << #x << "[" << hoge << "]: " << x[hoge].first<< " " << x[hoge].second << '\n'

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> Pii;
typedef vector<int> vint;
typedef vector<ll> vll;
const double INF = DBL_MAX;
const ll MOD = 998244353;

int K;
double dp[210];

int main(){
  cin >>K;
  repeat(c,100000){
    repeat(i,K){
      double tmp=1;
      repeat(j,6){
        int jj=i+1+j;
        if(jj==K)continue;
        if(jj>K)jj=0;
        tmp += dp[jj]/6;
      }
      swap(tmp,dp[i]);
    }
  }
  printf("%.8lf\n",dp[0]);
  return 0;
}