/* -*- coding: utf-8 -*-
 *
 * 1271.cc:  No.1271 初めての級数 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int CNT = 10000000;

/* typedef */

typedef long long ll;

/* global variables */

/* subroutines */

/* main */

int main() {
  int k;
  scanf("%d", &k);

  double sum = 0.0;
  if (k == 0) {
    for (int i = CNT; i >= 1; i--)
      sum += 1.0 / ((ll)i * i);
  }
  else {
    for (int i = 1; i <= k; i++) sum += 1.0 / i;
    sum /= k;
  }

  printf("%.16lf\n", sum);
  return 0;
}