#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <list>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <algorithm>
#include <functional>
#include <limits>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <climits>
#include <complex>

using namespace std;

#define INF (INT_MAX/3)
#define PI (2*acos(0.0))
#define EPS (1e-8)

typedef long long ll;
typedef unsigned long long ull;

double E[30];

int main(){
  ios_base::sync_with_stdio(0);
  int K; cin >> K;
  for(int x = K - 1; x >= 0; x--){
    E[x] = E[x+1] / 6 + E[x+2] / 6 + E[x+3] / 6 + E[x+4] / 6 + E[x+5] / 6 + E[x+6] / 6 + 1;
  }
  cout << E[0] << endl;
  return 0;
}