## https://yukicoder.me/problems/no/2111

MOD = 998244353

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

    answer = 0
    b = 0
    for i in range(N):
        a = A[i]

        ans1 = a * pow(2, N - 1 - i, MOD)
        ans1 %= MOD
        ans1 *= (pow(2, i, MOD) - 1) % MOD
        ans1 %= MOD

        ans2 = (b * pow(2, N - 1 - i, MOD)) % MOD

        answer += (ans2 - ans1) % MOD
        answer %= MOD

        b += (a * pow(2, i, MOD)) % MOD
        b %= MOD
    print(answer)





if __name__ == "__main__":
    main()