#!/usr/bin/env python3
MOD = 998244353
def main():
    N = int(input())
    A = list(map(int, input().split()))
    ans = 0
    for i in range(N):
        ans += -A[i] * (2 ** i - 1) + A[i] * (2 ** (N - 1 - i) - 1)
        ans %= MOD
    print(ans)
    return

if __name__ == '__main__':
    main()