#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
#include <stdio.h>
#include <queue>
#include <deque>
#include <cstdio>
#include <set>
#include <map>
#include <bitset>
#include <stack>
#include <cctype>
using namespace std;
long long a[500050];
long long mod = 998244353;
int main() {
	long long n;
	cin >> n;
	for (int i = 0; i < n; i++) {
		cin >> a[i];
	}
	long long t = 1;
	for (int i = 0; i < n - 2; i++) {
		t *= 2;
		t %= mod;
	}
	long long ans = 0, t1 = t;
	for (int i = 0; i < n; i++) {
		t1 += t;
		t1 %= mod;
		ans += t1 * a[i] % mod;
		ans %= mod;
	}
	cout << ans << endl;
}