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

#define rep(i, n) for (int i = 0; i < (int)(n); i++)

int main()
{
    long long X;
    cin >> X;
    vector<atcoder::modint998244353> Y(X);
    rep(i, X)
    {
        long long y;
        cin >> y;
        Y[i] = y;
    }

    atcoder::modint998244353 sum_dist_from_0 = 0;
    atcoder::modint998244353 v_cnt = 1;

    // 項数n,初項a0,公差dのときの総和
    auto f = [&](atcoder::modint998244353 n, atcoder::modint998244353 a0, atcoder::modint998244353 d) -> atcoder::modint998244353
    {
        return n * (2 * a0 + (n - 1) * d) / 2;
    };

    auto f2 = [&](atcoder::modint998244353 n) -> atcoder::modint998244353
    {
        return n * (n + 1) * (2 * n + 1) / 6;
    };

    atcoder::modint998244353 ans = 0;
    for (auto y : Y)
    {
        /*
        atcoder::modint998244353 val = sum_dist_from_0;
        rep(i, y.val())
        {
            val += v_cnt + i;
            ans += val;
        }
        */

        atcoder::modint998244353 val1 = sum_dist_from_0 * y;
        atcoder::modint998244353 val2 = f(y, 1, 1) * v_cnt;
        atcoder::modint998244353 val3 = (f2(y) - f(y, 1, 1)) / 2;

        ans += val1 + val2 + val3;

        sum_dist_from_0 += y * (y + 1) / 2;
        v_cnt += y;
    }

    cout << ans.val() << endl;

    return 0;
}