#include <bits/stdc++.h>
using namespace std;

int main()
{
	int64_t n;
	cin >> n;
	vector<int64_t> a(n);
	for(int64_t i = 0; i < n; i++) cin >> a[i];
	const int64_t mod = 998244353;
	
	vector<int64_t> b(n - 1);
	for(int64_t i = 0; i < n - 1; i++) b[i] = (a[i] - a[i + 1] + mod) % mod;
	vector<int64_t> pow2(n + 1);
	pow2[1] = 2;
	for(int64_t i = 2; i <= n; i++)
	{
		pow2[i] = pow2[i - 1] * 2;
		pow2[i] %= mod;
	}
	
	vector<int64_t> c(n - 1);
	for(int64_t i = 1; i <= n - 1; i++)
	{
		c[i - 1] = (pow2[i] - 1) * (pow2[n - i] - 1);
		c[i - 1] %= mod;
	}
	
	int64_t ans = 0;
	for(int64_t i = 0; i < n - 1; i++)
	{
		ans += b[i] * c[i];
		ans %= mod;
	}
	cout << ans << endl;
	return 0;
}