#include <bits/stdc++.h>
using namespace std;

#define int long long
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define repi(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define all(x) (x).begin(),(x).end()
#define pb push_back
#define mp make_pair
#define mt make_tuple

typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;

const int inf = 1LL<<60;
const int mod = 1e9 + 7;
const double eps = 1e-9;

/*{
}*/

signed main()
{
  int k;
  cin >> k;

  vector<double> E(k+6, 1);
  rep(i, 6) E[k+i] = 0;
  
  for(int i = k-1; i >= 0; i--){
    rep(j, 6){
      E[i] += E[i+j+1]/6.0;
    }
  }

  printf("%.9f\n", E[0]);

  return 0;
}