MOD = 998244353

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

pow2 = [1 for _ in range(n)]
for i in range(1, n):
  pow2[i] = (pow2[i - 1] * 2) % MOD

ans = 0
for i in range(n):
  ans = (ans + a[i] * (pow2[n - 1 - i] - pow2[i])) % MOD

print(ans)