N = int(input())
A = list(map(int, input().split()))
ans = 0
MOD = 998244353
B = [0] * N
tmp = 1
for i in range(1,N):
    B[i] = tmp + B[i-1]
    B[i] %= MOD
    tmp *= 2
    tmp %= MOD
for i in range(N):
    ans += (B[N-1-i] - B[i]) * A[i]
    ans %= MOD
print(ans)