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

using ll = long long;
using pii = pair<int, int>;
template <class T>
using V = vector<T>;
template <class T>
using VV = V<V<T>>;

#define pb push_back
#define eb emplace_back
#define mp make_pair
#define fi first
#define se second
#define rep(i, n) rep2(i, 0, n)
#define rep2(i, m, n) for (int i = m; i < (n); i++)
#define per(i, b) per2(i, 0, b)
#define per2(i, a, b) for (int i = int(b) - 1; i >= int(a); i--)
#define ALL(c) (c).begin(), (c).end()
#define SZ(x) ((int)(x).size())

constexpr ll TEN(int n) { return (n == 0) ? 1 : 10 * TEN(n - 1); }

template <class T, class U>
void chmin(T& t, const U& u) {
    if (t > u) t = u;
}
template <class T, class U>
void chmax(T& t, const U& u) {
    if (t < u) t = u;
}

template <class T, class U>
ostream& operator<<(ostream& os, const pair<T, U>& p) {
    os << "(" << p.first << "," << p.second << ")";
    return os;
}

template <class T>
ostream& operator<<(ostream& os, const vector<T>& v) {
    os << "{";
    rep(i, v.size()) {
        if (i) os << ",";
        os << v[i];
    }
    os << "}";
    return os;
}

#ifdef LOCAL
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
    cerr << " " << H;
    debug_out(T...);
}
#define debug(...) \
    cerr << __LINE__ << " [" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#define dump(x) cerr << __LINE__ << " " << #x << " = " << (x) << endl
#else
#define debug(...) (void(0))
#define dump(x) (void(0))
#endif

template <unsigned int MOD>
struct ModInt {
    using uint = unsigned int;
    using ull = unsigned long long;
    using M = ModInt;

    uint v;

    ModInt(ll _v = 0) { set_norm(_v % MOD + MOD); }
    M& set_norm(uint _v) {  //[0, MOD * 2)->[0, MOD)
        v = (_v < MOD) ? _v : _v - MOD;
        return *this;
    }

    explicit operator bool() const { return v != 0; }
    M operator+(const M& a) const { return M().set_norm(v + a.v); }
    M operator-(const M& a) const { return M().set_norm(v + MOD - a.v); }
    M operator*(const M& a) const { return M().set_norm(ull(v) * a.v % MOD); }
    M operator/(const M& a) const { return *this * a.inv(); }
    M& operator+=(const M& a) { return *this = *this + a; }
    M& operator-=(const M& a) { return *this = *this - a; }
    M& operator*=(const M& a) { return *this = *this * a; }
    M& operator/=(const M& a) { return *this = *this / a; }
    M operator-() const { return M() - *this; }
    M& operator++(int) { return *this = *this + 1; }
    M& operator--(int) { return *this = *this - 1; }

    M pow(ll n) const {
        if (n < 0) return inv().pow(-n);
        M x = *this, res = 1;
        while (n) {
            if (n & 1) res *= x;
            x *= x;
            n >>= 1;
        }
        return res;
    }

    M inv() const {
        ll a = v, b = MOD, p = 1, q = 0, t;
        while (b != 0) {
            t = a / b;
            swap(a -= t * b, b);
            swap(p -= t * q, q);
        }
        return M(p);
    }

    bool operator==(const M& a) const { return v == a.v; }
    bool operator!=(const M& a) const { return v != a.v; }
    friend ostream& operator<<(ostream& os, const M& a) { return os << a.v; }
    static uint get_mod() { return MOD; }
};

using Mint = ModInt<998244353>;

template <class T>
struct BIT {
    int n;
    vector<T> bit;

    BIT(int _n = 0) : n(_n), bit(n + 1) {}

    // sum of [0, i), 0 <= i <= n
    T sum(int i) {
        T s = 0;
        while (i > 0) {
            s += bit[i];
            i -= i & -i;
        }
        return s;
    }

    // 0 <= i < n
    void add(int i, T x) {
        ++i;
        while (i <= n) {
            bit[i] += x;
            i += i & -i;
        }
    }

    //[l, r) 0 <= l < r < n
    T sum(int l, int r) { return sum(r) - sum(l); }

    // not verified

    // smallest i, sum(i) >= w, none -> n + 1
    int lower_bound(T w) {
        if (w <= 0) return 0;
        int x = 0, l = 1;
        while (l * 2 <= n) l *= 2;

        for (int k = l; k > 0; k /= 2) {
            if (x + k <= n && bit[x + k] < w) {
                w -= bit[x + k];
                x += k;
            }
        }
        return x + 1;
    }
};

const int MX = 2510;

int main() {
    int N;
    cin >> N;
    V<int> A(N);
    rep(i, N) cin >> A[i];
    V<Mint> ans(MX);
    int md = -1;
    rep(i, N - 1) chmax(md, A[i + 1] - A[i]);

    for (int d = md; d < MX; ++d) {
        V<Mint> dp(N + 1);
        dp[0] = 2;
        Mint cur_sum;
        int p = 0;

        for (int i = 1; i < N - 1; ++i) {
            Mint s;
            while (p < i - 1 && A[p] < A[i] - d) {
                cur_sum -= dp[p + 1];
                dp[p + 1] = 0;
                p++;
            }

            dp[i] = cur_sum + 2;
            cur_sum += dp[i];
        }

        Mint s = 2;
        for (int j = 0; j < N - 1; ++j) {
            if (A[N - 1] - A[j] <= d) {
                s += dp[j + 1];
            }
        }
        //  debug(d, dp, s);
        ans[d] = s;
    }

    Mint a;
    for (int d = md; d < MX; ++d) {
        a += (ans[d] - ans[d - 1]) * d;
    }
    cout << a << endl;

    return 0;
}