#include <bits/stdc++.h>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;
typedef unsigned long long ull;

struct ST {
  double a, b;
  ST():a(0),b(0){}
  ST(double a, double b):a(a),b(b){}
  ST operator+=(const ST& x){
    a += x.a;
    b += x.b;
    return *this;
  }
  ST operator-=(const ST& x){
    a -= x.a;
    b -= x.b;
    return *this;
  }
  ST operator/=(double x){
    a /= x;
    b /= x;
    return *this;
  }
};

int main(){
  int K;
  cin >> K;
  vector<ST> dp(K+10);
  REP(i,K+1,K+10) dp[i] = ST(1,0);

  for(int i=K-1; i>=0; i--){
    ST sum;
    rep(j,6){
      sum += dp[i+1+j];
    }
    sum /= 6;
    sum += ST(0,1);
    dp[i] = sum;
  }

  double a = dp[0].a;
  double b = dp[0].b;
  double ret = b / (1-a);

  cout << fixed << setprecision(16) << ret << endl;
  
  return 0;
}