#include "testlib.h"
#include <atcoder/modint.hpp>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define lint long long
using mint = modint998244353;

mint solve(vector<lint> p) {
    lint n = p.size();
    mint ans = 1;
    rep(i, n) for (lint j = i + 1; j < n; ++j) { ans *= p[j] - p[i] + (j - i); }
    mint fact = 1;
    for (int i = 1; i < n; ++i) {
        fact *= i;
        ans /= fact;
    }
    return ans;
}

int main(int argc, char *argv[]) {
    registerValidation(argc, argv);
    int n = inf.readInt(1, 5000, "n");
    vector<lint> p(n);
    inf.readEoln();
    rep(i, n) {
        if (i) {
            inf.readSpace();
        }
        p[i] = inf.readInt(1, 1'000'000'000, "p_i");
    }
    inf.readEoln();
    inf.readEof();
    rep(i, n - 1) { assert(p[i] <= p[i + 1]); }
    vector<lint> q(n);
    rep(i, n) q[n - 1 - i] = p.back() - p[i] + 1;
    cout << (solve(p) * solve(q)).val() << endl;
}