from collections import *
from itertools import *
from functools import *
from heapq import *
import sys,math
input = sys.stdin.readline

mod = 998244353
N = int(input())
A = list(map(int,input().split()))
ans = 0
ans += A[0]*(pow(2,N-1,mod)-1)
for i in range(1,N-1):
    ans += A[i]*pow(2,i-1,mod)*pow(2,N-i-1,mod)
    ans %= mod

A.reverse()
ans -= A[0]*(pow(2,N-1,mod)-1)
for i in range(1,N-1):
    ans -= A[i]*pow(2,i-1,mod)*pow(2,N-i-1,mod)
    ans %= mod

print(ans%mod)