#include <bits/stdc++.h>

using namespace std;

// using mint = long double;
// using mint = modint998244353;
// using mint = modint1000000007;

typedef long long ll;
typedef pair<ll, ll> P;
typedef pair<P, ll> T;
typedef pair<ll, vector<ll>> Pd;

const ll INF = 1e18;
const ll fact_table = 3200008;

priority_queue <ll> pql;
priority_queue <P> pqp;
//big priority queue
priority_queue <ll, vector<ll>, greater<ll> > pqls;
priority_queue <P, vector<P>, greater<P> > pqps;
//small priority queue
//top pop

ll dx[8] = {1, 0, -1, 0, 1, 1, -1, -1};
ll dy[8] = {0, 1, 0, -1, -1, 1, 1, -1};
//↓,→,↑,←

/*
#define endl "\n"
#ifdef ENJAPMA
#undef endl
#endif
*/

#define p(x) cout<<x<<endl;
#define el cout<<endl;
#define pe(x) cout<<x<<" ";
#define ps(x) cout<<fixed<<setprecision(25)<<x<<endl;
#define pu(x) cout<<(x);
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define pc(x) cout << x << ",";
#define rep(i, n) for (ll i = 0; i < (n); i ++)
#define rep2(i, a, b) for (ll i = a; i <= (b); i++)
#define rep3(i, a, b) for (ll i = a; i >= (b); i--)

typedef vector<ll> vec;
typedef vector<vector<ll>> mat;

const ll mod = 998244353ll;
// const ll mod = 1000000007ll;

ll mypow(ll a, ll b, ll m = mod) {ll x = 1; while (b) {while (!(b & 1)) {(a *= a) %= m; b >>= 1;}(x *= a) %= m; b--;} return x;}
vec readvec(ll read) { vec res(read); for (int i = 0; i < read; i++) { cin >> res[i]; } return res;}
void YES(bool cond) { if (cond) { p("YES");} else { p("NO");} return;}
void Yes(bool cond) { if (cond) { p("Yes");} else { p("No");} return;}
void line() { p("--------------------"); return;}

/*
ll fact[fact_table + 5], rfact[fact_table + 5];

void c3_init() {
    fact[0] = rfact[0] = 1;
    for (ll i = 1; i <= fact_table; i++) {
        fact[i] = (fact[i - 1] * i) % mod;
    }
    rfact[fact_table] = mypow(fact[fact_table], mod - 2, mod);
    for (ll i = fact_table; i >= 1; i--) {
        rfact[i - 1] = rfact[i] * i;
        rfact[i - 1] %= mod;
    }
    return;
}
ll c3(ll n, ll r) {
    return (((fact[n] * rfact[r]) % mod ) * rfact[n - r]) % mod;
}
*/

bool icpc = false;
bool multicase = false;

ll n;
ll x[2505], xsum[2505];
ll dp[2505];
ll table[2505];

bool solve() {
    cin >> n;
    for (int i = 1; i <= n; i++) {
        cin >> x[i];
    }
    reverse(x + 1, x + n + 1);
    dp[2] = 1;
    for (int d = 1; d <= 2500; d++) {
        bool ok = true;
        for (int i = 1; i < n; i++) {
            if (x[i] - x[i + 1] > d) ok = false;
        }
        if (!ok) {
            table[d] = 0;
            continue;
        }
        for (int i = 0; i <= n; i++) {
            dp[i] = xsum[i] = 0;
        }
        dp[2] = xsum[2] = 2;
        for (int i = 3; i <= n; i++) {
            ll ok = i, ng = 1;
            while (ok - ng > 1) {
                ll mid = (ok + ng) / 2;
                if (abs(x[mid - 1] - x[i]) <= d) {
                    ok = mid;
                } else {
                    ng = mid;
                }
            }
            dp[i] = xsum[i - 1] + (mod - xsum[ok - 1]);
            dp[i] %= mod;
            xsum[i] = xsum[i - 1] + dp[i];
            xsum[i] %= mod;
        }
        ll ans = xsum[n];
        table[d] = ans;
    }
    ll ans = 0;
    for (int i = 1; i <= 2500; i++) {
        ll r = table[i] + mod - table[i - 1];
        ans += (r * i) % mod;
        ans %= mod;
    }
    p(ans);
    return true;
}

int main() {

    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    if (icpc) {
        while (solve());
        return 0;
    }
    ll q, testcase = 1;
    if (multicase) {
        cin >> q;
    } else {
        q = 1;
    }
    while (q--) {
        // pu("Case ");pu("#");pu(testcase);pu(": ");
        solve();
        testcase++;
    }

// solve();
    return 0;
}