#include <iostream>
#include <cstdio>
#include <algorithm>
#include <string>
#include <vector>
#include <queue>
#include <set>
#include <numeric>
#include <cmath>
#include <map>
#define ll long long
#define endl '\n'
using namespace std;
// category : 

int main() {
    ios_base::sync_with_stdio(false);
    
    int n; cin>>n;
    ll a[n+1], ans=0;

    for(int i=1;i<=n;i++) cin>>a[i];

    for(int i=1;i<=n;i++){
        ans += a[i] * (pow(2,n-i) - pow(2,i-1));
    }
    cout<<(ans+998244353)%998244353<<endl;

	return 0;
}