n = int(input()); z = 998244353
a = list(map(int,input().split())); b = [2*(n+1)]
for i in range((n-1)//2): b.append(b[-1]+n-2-2*i)
b += b[:n//2][::-1]
print(sum(u*v for u,v in zip(a,b))*pow(2,n-3,z)%z)