import java.io.*; import java.util.*; import java.util.function.*; import java.util.stream.*; public class Main { static final int MOD = 998244353; public static void main(String[] args) throws Exception { Scanner sc = new Scanner(); int n = sc.nextInt(); int[] values = new int[n]; long[] twoes = new long[n + 1]; twoes[0] = 1; for (int i = 0; i < n; i++) { values[i] = sc.nextInt(); twoes[i + 1] = (twoes[i] * 2) % MOD; } long ans = 0; for (int i = 0; i < n; i++) { ans += values[i] * ((twoes[n - i - 1] - twoes[i] + MOD) % MOD) % MOD; ans %= MOD; } System.out.println(ans); } } class Scanner { BufferedReader br; StringTokenizer st = new StringTokenizer(""); StringBuilder sb = new StringBuilder(); public Scanner() { try { br = new BufferedReader(new InputStreamReader(System.in)); } catch (Exception e) { } } public int nextInt() { return Integer.parseInt(next()); } public long nextLong() { return Long.parseLong(next()); } public double nextDouble() { return Double.parseDouble(next()); } public String next() { try { while (!st.hasMoreTokens()) { st = new StringTokenizer(br.readLine()); } } catch (Exception e) { e.printStackTrace(); } finally { return st.nextToken(); } } }