#include <bits/stdc++.h>
using namespace std;
using i64 = int64_t;
using u64 = uint64_t;
using u8 = uint8_t;
using i8 = int8_t;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  double s = 0.0;
  for (int i = 1; i <= n; ++i) {
    s += (double)1 / i;
  }
  cout << s;
  return 0;
}
