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

P = 998244353
ans = 0
sub = a[0]
for i in range(1,N):
    tmp = a[i] * (pow(2,i,P)-1) % P
    ans += pow(2,N - i - 1,P) * (tmp - sub) % P
    sub += a[i] * pow(2,i,P)
    sub %= P
    ans %= P
    #print(ans,sub)
print((-ans)%P)