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

// 0-indexed
template <class T>
struct SegmentTree {
  // a,b,c: T, e:T(unit)
  // abc = (ab)c = a(bc)
  // ae = ea = a
  typedef function<T(T, T)> F;
  int n;
  F f;
  T unit;
  vector<T> dat;
  SegmentTree(){};
  SegmentTree(int newn, F f, T t) : f(f), unit(t) { init(newn); }
  SegmentTree(const vector<T> &v, F f, T t) : f(f), unit(t) {
    int _n = v.size();
    init(v.size());
    for (int i = 0; i < _n; ++i) dat[n + i] = v[i];
    for (int i = n - 1; i; --i) dat[i] = f(dat[i << 1], dat[(i << 1) | 1]);
  }
  void init(int newn) {
    n = 1;
    while (n < newn) n <<= 1;
    dat.assign(n << 1, unit);
  }

  // "go up" process
  void update(int k, T newdata) {
    dat[k += n] = newdata;
    while (k >>= 1) {
      dat[k] = f(dat[(k << 1) | 0], dat[(k << 1) | 1]);
    }
  }
  // [a,b)
  T query(int a, int b) {
    T vl = unit, vr = unit;
    for (int l = a + n, r = b + n; l < r; l >>= 1, r >>= 1) {
      if (l & 1) vl = f(vl, dat[l++]);
      if (r & 1) vr = f(dat[--r], vr);
    }
    return f(vl, vr);
  }
};

template <int mod = (int)(998244353)>
struct ModInt {
  int x;
  constexpr ModInt() : x(0) {}
  constexpr ModInt(int64_t y)
      : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}
  constexpr ModInt &operator+=(const ModInt &p) noexcept {
    if ((x += p.x) >= mod) x -= mod;
    return *this;
  }
  constexpr ModInt &operator-=(const ModInt &p) noexcept {
    if ((x += mod - p.x) >= mod) x -= mod;
    return *this;
  }
  constexpr ModInt &operator*=(const ModInt &p) noexcept {
    x = (int)(1LL * x * p.x % mod);
    return *this;
  }
  constexpr ModInt &operator/=(const ModInt &p) noexcept {
    *this *= p.inverse();
    return *this;
  }
  constexpr ModInt operator-() const { return ModInt(-x); }
  constexpr ModInt operator+(const ModInt &p) const noexcept {
    return ModInt(*this) += p;
  }
  constexpr ModInt operator-(const ModInt &p) const noexcept {
    return ModInt(*this) -= p;
  }
  constexpr ModInt operator*(const ModInt &p) const noexcept {
    return ModInt(*this) *= p;
  }
  constexpr ModInt operator/(const ModInt &p) const noexcept {
    return ModInt(*this) /= p;
  }
  constexpr bool operator==(const ModInt &p) const noexcept { return x == p.x; }
  constexpr bool operator!=(const ModInt &p) const noexcept { return x != p.x; }
  constexpr ModInt inverse() const noexcept {
    int a = x, b = mod, u = 1, v = 0, t = 0;
    while (b > 0) {
      t = a / b;
      swap(a -= t * b, b);
      swap(u -= t * v, v);
    }
    return ModInt(u);
  }
  constexpr ModInt pow(int64_t n) const {
    ModInt res(1), mul(x);
    while (n) {
      if (n & 1) res *= mul;
      mul *= mul;
      n >>= 1;
    }
    return res;
  }
  friend constexpr ostream &operator<<(ostream &os, const ModInt &p) noexcept {
    return os << p.x;
  }
  friend constexpr istream &operator>>(istream &is, ModInt &a) noexcept {
    int64_t t = 0;
    is >> t;
    a = ModInt<mod>(t);
    return (is);
  }
  constexpr int get_mod() { return mod; }
};
using mint = ModInt<>;

int n;
vector<int> a;
vector<mint> cnt;

mint solve();

int main() {
  cin >> n;
  a.resize(n);
  for (auto &p : a) cin >> p;
  cout << solve() << endl;
  return 0;
}

mint solve() {
  if (n == 2) return 2 * (a[1] - a[0]);
  mint res = 0;
  cnt.assign(2501, 0);
  a.push_back(a[n - 1]);
  for (int x = 1; x <= 2500; ++x) {
    vector<int> memo(n, 0);
    for (int i = 0; i < n; ++i) {
      int fi = i;
      memo[i] = i;
      while (i + 1 < n && a[i + 1] - a[i] <= x) memo[++i] = fi;
    }
    SegmentTree<mint> seg[2];
    auto f = [](mint l, mint r) { return l + r; };
    for (int i = 0; i < 2; ++i) seg[i] = SegmentTree<mint>(n + 1, f, 0);
    seg[0].update(0, 1);
    seg[1].update(0, 1);
    for (int i = 0; i < n; ++i)
      for (int j = 0; j < 2; ++j) {
        int l = memo[i],
            r = (int)(lower_bound(a.begin(), a.end(), a[i + 1] - x) -
                      a.begin()) +
                1;
        l = max(l, r);
        mint now = memo[i] == 0;
        if (l < i + 1) now += seg[1 ^ j].query(l, i + 1);
        seg[j].update(i + 1, now);
      }
    cnt[x] = seg[0].query(n, n + 1) + seg[1].query(n, n + 1);
    res += (cnt[x] - cnt[x - 1]) * x;
  }
  return res / 2;
}