from re import A
import sys
#input = sys.stdin.readline
#input = sys.stdin.buffer.readline #文字列はダメ
#sys.setrecursionlimit(1000000)
#import math
import bisect
#import itertools
#import random
#from heapq import heapify, heappop, heappush
from collections import defaultdict
#from collections import deque
#import copy #DeepCopy: hoge = [_[:] for _ in hogehoge]
#from functools import lru_cache
#@lru_cache(maxsize=None)
#MOD = pow(10,9) + 7
MOD = 998244353
#dx = [1,0,-1,0]
#dy = [0,1,0,-1]
#dx8 = [1,1,0,-1,-1,-1,0,1]
#dy8 = [0,1,1,1,0,-1,-1,-1]

twos = [1]
for i in range(500000):
    twos.append(twos[-1]*2%MOD)

def main():
    N = int(input())
    A = list(map(int,input().split()))

    ans = 0
    for i,a in enumerate(A):
        left = i
        right = N - (i+1)
        temp = (twos[right] - twos[left]) * a
        # print(temp)
        ans += temp%MOD
        ans %= MOD
    
    print(ans)


if __name__ == '__main__':
    main()