#include <iostream>
#include <vector>
#include <cmath>
#include <map>
#include <set>
#include <iomanip>
#include <queue>
#include <algorithm>
#include <numeric>
#include <deque>

using namespace std;
using ll = long long;
const ll modc = 998244353;

long long mod_exp(long long b, long long e, long long m){
    if (e > 0 && b == 0) return 0;
    long long ans = 1;
    b %= m;

    while (e > 0){
        if ((e & 1LL)) ans = (ans * b) % m;
        e = e >> 1LL;
        b = (b*b) % m;
    }

    return ans;
}


int main(){

    ll N, ans=0, A;
    cin >> N;
    for (int i=1; i<=N; i++){
        cin >> A;
        ans += A * (mod_exp(2, N-i, modc)-1) % modc;
        ans %= modc;
        ans += modc - A * (mod_exp(2, i-1, modc)-1) % modc;
        ans %= modc;
    }

    cout << ans << endl;

    return 0;
}