#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<ll> VL;
typedef vector<VL> VVL;
typedef pair<int, int> PII;

#define FOR(i, a, n) for (int i = (int)a; i < (int)n; ++i)
#define REP(i, n) FOR(i, 0, n)
#define ALL(x) x.begin(), x.end()
#define MOD 1000000007
#define INF 1000000000
#define PI 3.14159265359
#define EPS 1e-12

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

  double e[30];
  e[k-1] = 1;
  FOR(i, k, k+5) e[i] = 0;

  for(int i=k-2; i>=0; i--) {
    e[i] = (e[i+1] + e[i+2] + e[i+3] + e[i+4] + e[i+5] + e[i+6])/6 + 1;
  }

  cout << fixed << setprecision(8) << e[0] << endl;

  return 0;
}