N = int(input())
a = list(map(int,input().split()))
mod = 998244353
n2 = [0]*(N+1)
n2[0] = 1
ans =0
for i in range(1,N+1):
  n2[i] = (2*n2[i-1])%mod

for i in range(N):
  ai = a[i]
  ans = (ans-ai*(n2[i]-1)+ai*(n2[N-i-1]-1))%mod
print(ans)