import sys
input = sys.stdin.readline

N=int(input())
A=list(map(int,input().split()))
MOD=998244353

pw=[0]
p=1
for i in range(N-1):
    p<<=1
    p%=MOD
    pw.append(p-1)

ans=0
for i in range(N):
    ans += A[i] * (pw[N-i-1] - pw[i]) % MOD
    ans %= MOD
print(ans)