import java.util.*;
import java.lang.*;
import java.io.*;

class Ideone{
	public static void main (String[] args) throws java.lang.Exception{
		double k;
		double d = 0;
		int b=1;
		Scanner x = new Scanner(System.in);
		int n=x.nextInt();
		for (int i=1;i<=n;i++){
			k = x.nextDouble();
			k/=b;
			b*=i;
			d+=k;
		}
		System.out.print(d);
	}
}