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


two = [1] * (N + 10)
for i in range(1, N + 10):
    two[i] = two[i-1] * 2 % mod

ans = 0
for i, a in enumerate(A):
    ans += a * (two[N - i - 1] - 1) % mod
    ans -= a * (two[i] - 1) % mod
    ans %= mod
print(ans)