#include <bits/stdc++.h>
#pragma GCC optimize("O3", "unroll-loops")
#pragma GCC target("avx2")
using namespace std;
long long int power(long long int x, long long int y) {
  long long int res = 1;
  x = x % 1000000007;
  while (y > 0) {
    if (y & 1) res = (res * x) % 1000000007;
    y = y >> 1;
    x = (x * x) % 1000000007;
  }
  return res;
}
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long int n;
  cin >> n;
  long double ans = 0.000, x = 0.00, y;
  for (long long int i = 1; i <= n; i++) {
    x = (long double)i;
    ans = (ans + (long double)1 / x);
  }
  cout << fixed << setprecision(10) << ans;
}
