#include <bits/stdc++.h>
using namespace std;
int main() { 
    int n, tmp;
    double ans, num ;
    cin >> n;
    ans = 0.0;
    
    for (int i = 1; i <= n; i++) {
        double ii = 1.0 * i;
        cin >> tmp;
        num = 1.0 / ii;
        ans = (ans + num);
    }
    
    cout << fixed << setprecision(6) << ans << "\n";
	return 0;
}