#include<bits/stdc++.h>
using namespace std;
#ifdef LOCAL_DEBUG
  #include "LOCAL_DEBUG.hpp"
#endif
#define int long long

signed main(){

  int k; cin >> k;

  vector<double> dp(30, -1);
  dp[0] = 0;
  function< double(int) > rec =
  [&](int x){
    if(dp[x] != -1) return dp[x];
    dp[x] = 1;
    for(int j = 1; j <= 6; j++){
      if(x - j >= 0) dp[x] += rec(x - j) * 1.0 / 6;
    }
    return dp[x];
  };
  cout << rec(k) << endl;

  return 0;
}