#include <bits/stdc++.h>
using namespace std;

#ifdef _RUTHEN
#include <debug.hpp>
#else
#define show(...) true
#endif

using ll = long long;
#define rep(i, n) for (int i = 0; i < (n); i++)
template <class T> using V = vector<T>;

#include <atcoder/modint>
using mint = atcoder::modint998244353;

void solve() {
    int N;
    cin >> N;
    V<ll> A(N);
    rep(i, N) cin >> A[i];
    V<mint> p2(N);
    p2[0] = 1;
    rep(i, N - 1) p2[i + 1] = p2[i] * 2;
    mint ans = 0;
    rep(i, N) ans += A[i] * (p2[N - 1 - i] - 1);
    rep(i, N) ans -= A[i] * (p2[i] - 1);
    cout << ans.val() << '\n';
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int tt = 1;
    while (tt--) solve();
    return 0;
}