#include <bits/stdc++.h>
using namespace std;
long long mod = 1e9 + 7;
long long poww(long long x, long long y) {
  if (y == 0) return 1;
  if (x == 1) return 1;
  if (x == 0) return 0;
  if (y == 1) return x;
  long long d = poww(x, y / 2);
  d %= mod;
  if (y % 2) return (((d * d) % mod) * x) % mod;
  return (d * d) % mod;
}
int main() {
  long long n;
  cin >> n;
  double x, sum = 0;
  for (long long i = 1; i <= n; i++) {
    x = (double)1 / (double)i;
    sum += x;
  }
  cout << sum;
  return 0;
}
