using System.Numerics;
using System;

public class Hello
{
    public static int MOD = 1000000007;
    static void Main()
    {
        var n = int.Parse(Console.ReadLine().Trim());
        string[] line = Console.ReadLine().Trim().Split(' ');
        var a = Array.ConvertAll(line, int.Parse);
        getAns(n, a);
    }
    static void getAns(int n, int[] a)
    {
        var ans = 0L;
        var t = 1L;
        for (int i = 0; i < n; i++)
        {
            t *= a[i];
            t %= MOD;
            long t2;
            if (n - 2 - i < 0) t2 = 1L;
            else
            {
                t2 = (long)BigInteger.ModPow(3, n - 2 - i, MOD) * 2L;
                t2 %= MOD;
            }
            t2 *= t;
            t2 %= MOD;
            ans += t2;
            ans %= MOD;
        }
        Console.WriteLine(ans);
    }
}