from typing import List, Tuple, Callable, TypeVar
import sys
import itertools
import heapq
import math
import bisect
from collections import deque, defaultdict
from functools import lru_cache, cmp_to_key

input = sys.stdin.readline

# for AtCoder Easy test
if __file__ != 'prog.py':
    sys.setrecursionlimit(10 ** 6)


def readints(): return map(int, input().split())
def readlist(): return list(readints())
def readstr(): return input()[:-1]


N = int(input())
A = readlist()
mod = 998244353

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