#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
#define drep(i, cc, n) for (ll i = (cc); i <= (n); ++i)
#define rep(i, n) drep(i, 0, n - 1)
#define all(a) (a).begin(), (a).end()
#define pb push_back
#define fi first
#define se second

const ll MOD = 1000000007;
const ll MOD2 = 998244353;
const ll INF = 1LL << 60;
const ll MAX_N = 2e5;

ll pow_mod(ll x, ll n, ll mod){
    ll ret = 1;
    while(n > 0){
        if(n & 1) ret = (ret*x)%mod;
        x = x*x%mod;
        n >>=1;
    }
    return ret;
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    
    ll n; cin >> n;
    vector<ll> a(n); rep(i, n) cin >> a[i];

    ll mod = MOD2;
    ll ans = 0;
    rep(i, n){
        ll sa_plus = (pow_mod(2, i, mod)*(pow_mod(2, n-i-1, mod)-1))%mod;
        sa_plus = (sa_plus*a[i])%mod;
        ll sa_minus = ((pow_mod(2, i, mod)-1)*pow_mod(2, n-i-1, mod))%mod;
        sa_minus = (sa_minus*a[i])%mod;
        ans += (sa_plus - sa_minus + mod)%mod;
        ans %= mod;
    }

    cout << ans << endl;
}