#define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES

#include <iostream>
#include <cstring>
#include <algorithm>
#include <limits.h>
#include <cmath>
#include <cstdio>
#include <vector>
#include <set>
#include <string>
#define REP(i,a,b) for(i=a;i<b;i++)
#define rep(i,n) REP(i,0,n)
using namespace std;

typedef long long ll;
typedef unsigned long long ull;

int test = 0;
/* ここからが本編 */

int main(void)
{
  int i,j,k,l;
  int trialNum = 1000000;
  int K;
  int sum = 0;
  cin >> K;
  for(i=0;i<trialNum;i++) {
    int cnt = 0;
    int value = 0;
    while(value != K) {
      value += rand() % 6 + 1;
      cnt++;
      if(value > K) value = 0;
    }
    sum += cnt;
  }
  printf("%lf\n",(double)sum/trialNum);
  return 0;
}