#include <bits/stdc++.h>
using namespace std;
const long long MOD = 998244353;
int main(){
  int N;
  cin >> N;
  vector<long long> a(N);
  for (int i = 0; i < N; i++){
    cin >> a[i];
  }
  vector<long long> POW(N, 0);
  POW[0] = 1;
  for (int i = 0; i < N - 1; i++){
    POW[i + 1] = POW[i] * 2 % MOD;
  }
  long long ans = 0;
  for (int i = 0; i < N; i++){
    ans += a[i] * POW[i] % MOD * (POW[N - 1 - i] - 1) % MOD;
    ans %= MOD;
    ans += (MOD - a[i]) * POW[N - 1 - i] % MOD * (POW[i] - 1) % MOD;
    ans %= MOD;
  }
  cout << ans << endl;
}