using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static long[] NList => ReadLine().Split().Select(long.Parse).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = NN;
        var a = NList;
        var mod = 1_000_000_007;
        var mul = new long[n];
        mul[n - 1] = 1;
        mul[n - 2] = 2;
        for (var i = n - 3; i >= 0; --i) mul[i] = mul[i + 1] * 3 % mod;
        var tmp = (long)a[0];
        var ans = tmp * mul[0] % mod;
        for (var i = 1; i < n; ++i)
        {
            tmp = tmp * a[i] % mod;
            ans = (ans + tmp * mul[i]) % mod;
        }
        WriteLine(ans);
    }
}