#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for (long long i=0;i<(long long)(n);i++)
#define all(v) v.begin(),v.end()
using ll=long long;
using pll=pair<ll,ll>;
using tll=tuple<ll,ll,ll>;
const ll INF=(1ll<<60);
template<class T> void chmin(T &a,T b){
    if(a>b){
        a=b;
    }
}
template<class T> void chmax(T &a,T b){
    if(a<b){
        a=b;
    }
}
int main(){
    const ll mod=998244353;
    ll n;
    cin >> n;
    vector<ll> a(n);
    rep(i,n) cin >> a[i];
    vector<ll> r(n+1);
    r[0]=1;
    rep(i,n) r[i+1]=r[i]*2%mod;
    ll sum=0;
    vector<ll> v(n);
    rep(i,n-1){
        sum+=r[i];
        sum%=mod;
    }
    v[0]=sum;
    rep(i,n-1) v[i+1]=(v[i]-r[i]+mod)%mod;
    ll ans=0;
    rep(i,n){
        ans+=a[i]*v[i]%mod;
        ans%=mod;
    }
    reverse(all(v));
    rep(i,n){
        ans=(ans-a[i]*v[i]%mod+mod)%mod;
    }
    cout << ans << endl;
}