#include <bits/stdc++.h>
using namespace std;
template <class T>
inline bool chmax(T &a, T b)
{
    if (a < b)
    {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
inline bool chmin(T &a, T b)
{
    if (a > b)
    {
        a = b;
        return 1;
    }
    return 0;
}
typedef long long int ll;

#define ALL(v) (v).begin(), (v).end()
#define RALL(v) (v).rbegin(), (v).rend()
#define endl "\n"
const double EPS = 1e-7;
const int INF = 1 << 30;
const ll LLINF = 1LL << 60;
const double PI = acos(-1);
const int MOD = 998244353;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};

//-------------------------------------

const ll MAX = 2000000;

ll fac[MAX], finv[MAX], inv[MAX];

void COMinit() // 二項係数を求める時は前処理としてCOMinit()をする
{
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (ll i = 2; i < MAX; i++)
    {
        fac[i] = fac[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}

// 二項係数計算
ll COM(ll n, ll k)
{
    if (n < k)
        return 0;
    if (n < 0 || k < 0)
        return 0;
    return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}

ll pow_mod(ll n, ll k)
{
    if (k == 0)
    {
        return 1;
    }
    else if (k % 2 == 1)
    {
        return pow_mod(n, k - 1) * n % MOD;
    }
    else
    {
        ll t = pow_mod(n, k / 2);
        return t * t % MOD;
    }
}

int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    COMinit();
    ll n;
    cin >> n;
    vector<ll> x(n);
    for (ll i = 0; i < n; i++)
    {
        cin >> x[i];
    }
    ll ans = 0;
    for (ll i = 1; i <= n; i++)
    {
        (ans += pow_mod(2, n - i) * ((pow_mod(1 + x[i - 1], i) - pow_mod(1 + x[i - 1], i - 1) + MOD) % MOD)) %= MOD;
    }
    cout << ans << endl;
}
