import java.util.Scanner;
import java.util.ArrayList;
import java.math.BigDecimal; 
 
public class Main {
	public static void main (String[] args) {
		Scanner scanner = new Scanner(System.in);
		int n = scanner.nextInt();
		BigDecimal ans = new BigDecimal(0);
		ArrayList<BigDecimal> a = new ArrayList<BigDecimal>();
		for(int i=0; i<n; i++) {
			BigDecimal x = scanner.nextBigDecimal();
			a.add(x);
		}
		for(int i=0; i<n; i++) {
			BigDecimal w = a.get(i);		
			BigDecimal v = new BigDecimal(1); 
			ans = ans.add(w.add(v.divide(w, 15, BigDecimal.ROUND_HALF_UP)));
		}
		System.out.println(ans);
	}
}

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