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

class Program
{
    static long NN => long.Parse(ReadLine());
    static long[] NList => ReadLine().Split().Select(long.Parse).ToArray();
    static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = NN;
        var a = NList;
        var mod = 998_244_353;
        var mul = new long[n];
        mul[0] = 1;
        for (var i = 1; i < mul.Length; ++i) mul[i] = mul[i - 1] * 2 % mod;
        var sum = 0L;
        var res = 0L;
        for (var i = n - 2; i >= 0; --i)
        {
            sum = (sum + a[i + 1] * mul[n - i - 2] % mod) % mod;
            res = (res + (a[i] * (mul[n - i - 1] - 1 + mod) % mod - sum + mod) % mod * mul[i] % mod) % mod;
        }
        WriteLine(res);
    }
}