import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    static int solve(int[] A) {
        //  Return the sum of S(S(A)) modulo 10^9+7.
        int sum=0;
        for(int i=0;i<A.length;i++)
        {
            sum=sum+A[i];
        }
        int len=A.length;
        int k=2;
        for(int j=0;j<len-1;j++)
        {
            sum=(sum*k)+2;
            k=k+2;
        }
        return sum;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] a = new int[n];
        for(int a_i = 0; a_i < n; a_i++){
            a[a_i] = in.nextInt();
        }
        int result = solve(a);
        System.out.println(result);
        in.close();
    }
}