#include <bits/stdc++.h>
#include <atcoder/all>

typedef long long int ll;
typedef long double ld;

using namespace std;
using namespace atcoder;

#define inf 1010000000
#define llinf 1001000000000000000ll
#define pi 3.14159265358979
#define rep(i, n) for(ll i = 0; i < (n); i++)
#define rep1(i, n) for(ll i = 1; i <= (n); i++)
#define rep2(i,l,r) for(ll i = (l); i < (r); i++)
#define rng(a) a.begin(),a.end()
#define fi first
#define se second
#define pb push_back
#define eb emplace_back
#define pob pop_back
#define mp make_pair
#define st string
#define sz(x) (int)(x).size()
#define mems(x) memset(x, -1, sizeof(x));
#define pcnt __builtin_popcountll
#define _GLIBCXX_DEBUG

#define dame { puts("-1"); return 0;}
#define yes { puts("Yes"); return 0;}
#define no { puts("No"); return 0;}
#define ret(x) { cout<<(x)<<endl;}
#define yn {puts("Yes");}else{puts("No");}

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }

// srand((unsigned)time(NULL)); rand()を用いる際にmainの頭に置く
// clock()/CLOCKS_PER_SEC 秒数を知りたいときに用いる
#define mod 998244353
#define mod2 1000000007 //問題に応じて使う方を決める
using mint = modint998244353; // .val()で出力

using pl = pair<ll,ll>;
using ppl = pair<pl,ll>;
using V = vector<ll>;
using Graph = vector<vector<ll>>; //llをEdgeにする等,適宜書き換える
// G.assign(n, vector<pl>()); グローバル変数にGを置く時に置く

int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(20);
  ll n; cin >> n;
  ll a[n]; rep(i,n) cin >> a[i];
  
  ll t[n+1]; t[0] = 1;
  rep(i,n){
      t[i+1] = t[i]*2;
      t[i+1]%=mod;
  }
  mint ans = 0;
  rep(i,n){
      ans += a[i] * t[n-i-1];
      ans -= a[i] * t[i];
  }
  ret(ans.val());
}