#include <iostream>
using namespace std;
 
int main() {
	int n; 
	double a;
	cin >> n;
	double s = 0.0;
	for (int  i = 0; i < n; i++){
		cin >> a;
		for(int j = 1; j<=i; j++){
			a/= j*1.0;
		}
		s+=a;
	}
	cout << s <<"\n";
	return 0;
}