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

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