MOD = 998244353

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

# Precompute pow2 up to n-1 needed for N - i -1 where i ranges from 0 to n-1
max_pow = n - 1
pow2 = [1] * (max_pow + 1)  # pow2[0..max_pow]
for k in range(1, max_pow + 1):
    pow2[k] = (pow2[k-1] * 2) % MOD

sum_first = 0
sum_second = 0

for i in range(n):
    exponent = n - i - 1
    if exponent >= 0:
        term = (pow2[exponent] - 1) % MOD
        sum_first = (sum_first + a[i] * term) % MOD

for j in range(n):
    term = (pow2[j] - 1) % MOD
    sum_second = (sum_second + a[j] * term) % MOD

ans = (sum_first - sum_second) % MOD
print(ans)