N=int(input())
A=list(map(int, input().split()))
mod=998244353
D=[1]
for i in range(2*10**5):
  d=D[-1]*2
  d%=mod
  D.append(d)
ans=0
for i in range(N):
  a,b=(D[N-1-i]-1)%mod,(D[i]-1)%mod
  ans+=A[i]*((a-b)%mod)
  ans%=mod
print(ans)