#include <bits/stdc++.h>
const long long inf = 0x3f3f3f3f3f3f3f3LL;
const long long mod = (long long)1e9 + 7;
using namespace std;
template <class T>
void smin(T& a, T val) {
  if (a > val) a = val;
}
template <class T>
void smax(T& a, T val) {
  if (a < val) a = val;
}
const long long N = 5 * (long long)1e5 + 10;
long long n, a[N];
long double ans[N];
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  cin >> n;
  ans[1] = 1;
  for (long long i = 2; i <= n; ++i) {
    ans[i] = 1 / (long double)i + ans[i - 1];
  }
  cout << fixed << setprecision(15);
  cout << ans[n];
  return 0;
}
