using System.Linq;
using System.Collections.Generic;
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, long.Parse).ToList();
        getAns(a);
    }
    static void getAns(List<long> a)
    {
        while (a.Count() > 1) a = calc(a);
        Console.WriteLine(a[0]);
    }
    static List<long> calc(List<long> a)
    {
        var res = new List<long>();
        var acount = a.Count();
        for (int i = 0; i < acount - 1; i++)
            res.Add((a[i] + a[i + 1]) % MOD);
        return res;
    }
}