#include <bits/stdc++.h>
using namespace std;
const int MX1 = 2e3 + 2, MX2 = 1e7 + 2, lg1 = 30;
const long long md2 = 1e9 + 7;
const int imf1 = 1 << 31, inf1 = ~imf1;
const long long imf2 = -1e10, inf2 = 1e10;
long double x;
int main() {
  int n;
  cin >> n;
  for (int i = n; i >= 1; i--) {
    x += (1 / ((long double)i));
  }
  cout << fixed << setprecision(12) << x;
  return 0;
}
