MOD = 998244353
N = int(input())
A = list(map(int,input().split()))

ans = 0
for i in range(N):
    ans += A[i] * (pow(2,N-1-i,MOD) - 1)
    ans -= A[i] * (pow(2,i,MOD) - 1)
    ans %= MOD
print(ans)