import sys
input = lambda: sys.stdin.readline().rstrip()
mod = 998244353

#  -----------------------  #

n = int(input())
A = list(map(int, input().split()))

ans = 0
for i in range(n):
  ans += A[i] * (pow(2, n-i-1, mod) - pow(2, i, mod))
  ans %= mod
print(ans % mod)