#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<ll, ll>;
using Graph = vector<vector<ll>>;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
const int ddx[8] = {0, 1, 1, 1, 0, -1, -1, -1};
const int ddy[8] = {1, 1, 0, -1, -1, -1, 0, 1};
const ll MOD = 1000000007;
const ll INF = 1000000000000000000L;
void Main() {
  double N;
  cin >> N;
  double ans = 0;
  ll M = N;
  for (ll i = 0; i < (ll)(M); i++) {
    ans += 1.0 / N;
    N--;
  }
  cout << ans << '\n';
}
int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(15);
  Main();
  return 0;
}
