/* -*- coding: utf-8 -*-
 *
 * 2123.cc:  No.2123 Chalk Breaker - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_N = 5000;

/* typedef */

/* global variables */

double dp[MAX_N + 1];

/* subroutines */

/* main */

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

  dp[0] = 0.0;
  for (int l = 1; l <= n; l++) {
    double s = 0.0;
    for (int j = 0; j < l; j++) s += dp[j] + dp[l - 1 - j];
    dp[l] = 1.0 + s / l;
  }

  printf("%.12lf\n", dp[n]);
  return 0;
}