#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vll = vector<ll>;
using vvll = vector<vll>;
#define all(A) A.begin(),A.end()
#define rep(i, n) for (ll i = 0; i < (ll) (n); i++)
using pqr = priority_queue<pair<ll, ll>, vector<pair<ll, ll>>, greater<pair<ll, ll>>>;

template<class T>
bool chmax(T& p, T q, bool C = 1) {
    if (C == 0 && p == q) {
        return 1;
    }
    if (p < q) {
        p = q;
        return 1;
    }
    else {
        return 0;
    }
}

template<class T>
bool chmin(T& p, T q, bool C = 1) {
    if (C == 0 && p == q) {
        return 1;
    }
    if (p > q) {
        p = q;
        return 1;
    }
    else {
        return 0;
    }
}

ll gcd(ll(a), ll(b)) {
    if (b == 0)return a;
    ll c = a;
    while (a % b != 0) {
        c = a % b;
        a = b;
        b = c;
    }
    return b;
}
ll sqrtz(ll N) {
    ll L = 0;
    ll R = sqrt(N) + 10000;
    while (abs(R - L) > 1) {
        ll mid = (R + L) / 2;
        if (mid * mid <= N)L = mid;
        else R = mid;
    }
    return L;


}
struct fenwick_tree {
	ll n;
	vll bit;
	fenwick_tree(ll num) :bit(num + 1, 0) { n = num; }

	void add(ll i, ll w) {
		for (ll x = i+1; x <= n; x += x & -x) {
			bit[x-1] += w;
		}
	}

	ll sum(ll i) {
		ll ret = 0;
		for (ll x = i+1; x > 0; x -= x & -x) {
			ret += bit[x-1];
		}
		return ret;
	}

	ll sum(ll L, ll R) {
		return sum(R) - sum(L);
	}


};
ll TE(vll A) {
	ll res = 0;
	ll N = A.size();
	fenwick_tree fw(N);
	rep(i, N) {
		res += i - fw.sum(A[i]);
		fw.add(A[i], 1);
	}
	return res;
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    ll N;
    cin>>N;
    const ll mod=998244353;
    vll T(N+1,1);
    rep(i,N){
        T[i+1]=(T[i]*2)%mod;
    }
    ll an=0,a;
    rep(i,N){
        cin>>a;
        an+=a*(T[N-i-1]-T[i]);
        an%=mod;
    }
    if(an<0)an+=mod;
    cout<<an<<endl;

}