#include<bits/stdc++.h>
#define rep(i,a,b) for(int i=a;i<b;i++)
#define rrep(i,a,b) for(int i=a;i>=b;i--)
#define fore(i,a) for(auto &i:a)
#define all(x) (x).begin(),(x).end()
//#pragma GCC optimize ("-O3")
using namespace std;
void _main(); int main() { cin.tie(0); ios::sync_with_stdio(false); _main(); }
typedef long long ll; const int inf = INT_MAX / 2; const ll infl = 1LL << 60;
template<class T>bool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; }
//---------------------------------------------------------------------------------------------------
//---------------------------------------------------------------------------------------------------
//---------------------------------------------------------------------------------------------------
void _main(){
  double N;
  cin >> N;
  double ans = 0;
  rep(i,1,N)ans += 1.0*N/(N-i);
  printf("%.9f\n", ans);
  return;
}


#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <queue>
#include <utility>
#include <tuple>
#include <cmath>
#include <numeric>
#include <set>
#include <map>
#include <array>
#include <complex>
#include <iomanip>
#include <cassert>
using ll = long long;
using std::cin;
using std::cout;
using std::endl;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
const int inf = (int)1e9 + 7;
const long long INF = 1LL << 60;

void solve()
{
  using real = long double;
  int n; cin >> n;
  std::vector<real> dp(n + 1);
  for (int i = 1; i < n; ++i)
  {
    dp[i + 1] = (dp[i] + (real)n / (real)(n - i));
  }
  cout << std::fixed << std::setprecision(15) << dp[n] << "\n";
}
int main()
{
  std::cin.tie(nullptr);
  std::ios::sync_with_stdio(false);


  int kkt = 1;
  //cin >> kkt;
  while(kkt--)
    solve();
  return 0;
}
