#include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <cmath>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <bitset>
#include <cstring>
#include <deque>
#include <random>
using namespace std;
#define FOR(I,A,B) for(int I = (A); I < (B); ++I)
#define CLR(mat) memset(mat, 0, sizeof(mat))
typedef long long ll;
random_device rnd;
mt19937 mt(rnd());
uniform_int_distribution<> r(1,6); // 0 - 1 一様乱数
int main()
{
  ios::sync_with_stdio(false);
  cin.tie(0);
  int K; cin >> K;
  int times = 700000;
  int cnt = 0;
  FOR(i,0,times) {
    int sum = 0;
    while(sum != K) {
      sum += r(mt);
      if(sum > K) sum = 0;
      cnt++;
    }
  }
  cout << (double) cnt / times << endl;
}