def main():
    from sys import stdin, setrecursionlimit
    # setrecursionlimit(1000000)
    input = stdin.readline
    def iinput(): return int(input())
    def sinput(): return input().rstrip()
    def i0input(): return int(input()) - 1
    def linput(): return list(input().split())
    def liinput(): return list(map(int, input().split()))
    def miinput(): return map(int, input().split())
    def li0input(): return list(map(lambda x: int(x) - 1, input().split()))
    def mi0input(): return map(lambda x: int(x) - 1, input().split())
    INF = 1000000000000000000
    MOD = 998244353

    pow2 = [1]
    N = iinput()
    for _ in [0] * (2 * N + 1):
        pow2.append(pow2[-1] * 2 % MOD)
     
    ans = 0
    

    for i, a in enumerate(liinput()):
        ans += (pow2[N-i-1] - 1) * a % MOD
        ans %= MOD
        ans -= (pow2[i] - 1) * a % MOD
        ans %= MOD
    
    print(ans)
        
main()