#include<bits/stdc++.h>
using namespace std;
using Int = long long;
template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}


struct Precision{
  Precision(){
    cout<<fixed<<setprecision(12);
  }
}precision_beet;

//INSERT ABOVE HERE
signed main(){
  int k;
  cin>>k;
  const int MAX = 100;
  vector<double> dp(MAX,0);
  for(int i=k-1;i>=0;i--){
    dp[i]=1;
    for(int j=1;j<=6;j++) dp[i]+=dp[i+j]/6;
  }
  cout<<dp[0]<<endl;
  return 0;
}