MOD = 998244353

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

sum_part = 0
for i in range(n):
    sum_part = (sum_part + a[i] * (i + 2)) % MOD

if n >= 2:
    pow_val = pow(2, n - 2, MOD)
else:
    pow_val = pow(2, MOD - 2, MOD)

ans = (sum_part * pow_val) % MOD
print(ans)