#include <bits/stdc++.h>
using namespace std;
const int INF = 0x3f3f3f3f;
const long long int LINF = 0x3f3f3f3f3f3f3f3fll;
const long double pi = acos(-1);
const int MOD = 1e9 + 7;
int main() {
  int n, i;
  double ans = 0.0;
  scanf("%d", &n);
  for (i = 1; i <= n; i++) {
    ans += 1 / (float)i;
  }
  printf("%.6lf\n", ans);
  return 0;
}
