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