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

MOD = 998244353
total = 1
two = 1
goal = pow(2, N-2, MOD)
div = pow(2, MOD-2, MOD)
score = 0

if N >= 2:
    for i, a in enumerate(A, start=1):
        score += total * a * goal
        score %= MOD
        if i != N-1:
            goal *= div
            goal %= MOD
        total += two+total
        total %= MOD
        two *= 2
        two %= MOD
    print(score)

else:
    print(A[0])