mod = 998244353


def main():
    import sys
    input = sys.stdin.readline

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

    ans = 0
    for i, a in enumerate(A):
        ans = (ans + (a * (pow(2, N - i - 1, mod) - 1)) % mod) % mod
        ans = (ans - (a * (pow(2, i, mod) - 1)) % mod) % mod
    print(ans)


if __name__ == '__main__':
    main()