#include <algorithm>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <functional>
#include <iostream>
#include <map>
#include <memory>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>
 
using namespace std;
 
#define sz size()
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define all(c) (c).begin(), (c).end()
#define rep(i,a,b) for(int i=(a);i<(b);++i)
#define clr(a, b) memset((a), (b) ,sizeof(a))
 
#define MOD 1000000009

unsigned int xor128(void) { 
  static unsigned int x = 123456789;
  static unsigned int y = 362436069;
  static unsigned int z = 521288629;
  static unsigned int w = 88675123; 
  unsigned int t;
 
  t = x ^ (x << 11);
  x = y; y = z; z = w;
  return w = (w ^ (w >> 19)) ^ (t ^ (t >> 8)); 
}

int main(){
  int k;
  cin>>k;
  int total = 0;
  rep(i,0,10000000){
    int a = 0;
    int c = 0;
    for(;;){
      a+=xor128()%6+1;
      c++;
      if(a==k)break;
      if(a>k)a=0;
    }
    total+=c;
  }
  cout << 1.*total/10000000 << endl;
  return 0;
}

/*
モンテカルロ法
*/