MOD = 998244353

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

total = 0
for i in range(N):
    term = (i + 2) * (N - i + 1)
    total = (total + A[i] * term) % MOD

# Compute 2^(N-3) mod MOD
exponent = N - 3
if exponent >= 0:
    factor = pow(2, exponent, MOD)
else:
    # Compute inverse^abs(exponent)
    inv_two = pow(2, MOD-2, MOD)  # Modular inverse of 2
    factor = pow(inv_two, -exponent, MOD)

result = (total * factor) % MOD
print(result)