mod=998244353
n=int(input())
a=list(map(int,input().split()))

pow2=[1]
for i in range(n+10):
  pow2.append(pow2[-1]*2%mod)
ans=0
for i in range(n):
  ans+=a[i]*(pow2[i])%mod*(pow2[n-1-i]-1)%mod
  ans-=a[i]*(pow2[i]-1)%mod*(pow2[n-1-i])%mod
  ans%=mod
  
print(ans)