#include <bits/stdc++.h>
using namespace std;
using ll = long long;
ll const m = 998244353;
int main () {
    int N;
    ll A[200020];
    cin >> N;
    for (int i = 0; i < N; i ++) {
        cin >> A[i];
    }
    ll bi = 1;
    ll ans = 0;
    for (int i = 0; i < N; i ++) {
        ans -= (A[i] * (bi - 1)) % m;
        if (ans < 0) {
            ans += m;
        }
        ans += (A[N - i - 1] * (bi - 1)) % m;
        if (ans >= m) {
            ans -= m;
        }
        bi *= 2;
        bi %= m;
    }
    cout << ans << endl;
}