#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
using ll = long long;
constexpr int INF = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 998244353;
constexpr int dy[] = {1, 0, -1, 0}, dx[] = {0, -1, 0, 1};
constexpr int dy8[] = {1, 1, 0, -1, -1, -1, 0, 1}, dx8[] = {0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U> inline bool chmax(T &a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U> inline bool chmin(T &a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    std::cout << fixed << setprecision(20);
  }
} iosetup;

template <int MOD>
struct MInt {
  unsigned val;
  MInt(): val(0) {}
  MInt(long long x) : val(x >= 0 ? x % MOD : x % MOD + MOD) {}
  static int get_mod() { return MOD; }
  static void set_mod(int divisor) { assert(divisor == MOD); }
  MInt pow(long long exponent) const {
    MInt tmp = *this, res = 1;
    while (exponent > 0) {
      if (exponent & 1) res *= tmp;
      tmp *= tmp;
      exponent >>= 1;
    }
    return res;
  }
  MInt &operator+=(const MInt &x) { if((val += x.val) >= MOD) val -= MOD; return *this; }
  MInt &operator-=(const MInt &x) { if((val += MOD - x.val) >= MOD) val -= MOD; return *this; }
  MInt &operator*=(const MInt &x) { val = static_cast<unsigned long long>(val) * x.val % MOD; return *this; }
  MInt &operator/=(const MInt &x) {
    // assert(std::__gcd(static_cast<int>(x.val), MOD) == 1);
    unsigned a = x.val, b = MOD; int u = 1, v = 0;
    while (b) {
      unsigned tmp = a / b;
      std::swap(a -= tmp * b, b);
      std::swap(u -= tmp * v, v);
    }
    return *this *= u;
  }
  bool operator==(const MInt &x) const { return val == x.val; }
  bool operator!=(const MInt &x) const { return val != x.val; }
  bool operator<(const MInt &x) const { return val < x.val; }
  bool operator<=(const MInt &x) const { return val <= x.val; }
  bool operator>(const MInt &x) const { return val > x.val; }
  bool operator>=(const MInt &x) const { return val >= x.val; }
  MInt &operator++() { if (++val == MOD) val = 0; return *this; }
  MInt operator++(int) { MInt res = *this; ++*this; return res; }
  MInt &operator--() { val = (val == 0 ? MOD : val) - 1; return *this; }
  MInt operator--(int) { MInt res = *this; --*this; return res; }
  MInt operator+() const { return *this; }
  MInt operator-() const { return MInt(val ? MOD - val : 0); }
  MInt operator+(const MInt &x) const { return MInt(*this) += x; }
  MInt operator-(const MInt &x) const { return MInt(*this) -= x; }
  MInt operator*(const MInt &x) const { return MInt(*this) *= x; }
  MInt operator/(const MInt &x) const { return MInt(*this) /= x; }
  friend std::ostream &operator<<(std::ostream &os, const MInt &x) { return os << x.val; }
  friend std::istream &operator>>(std::istream &is, MInt &x) { long long val; is >> val; x = MInt(val); return is; }
};
namespace std { template <int MOD> MInt<MOD> abs(const MInt<MOD> &x) { return x; } }
template <int MOD>
struct Combinatorics {
  using ModInt = MInt<MOD>;
  int val;  // "val!" and "mod" must be disjoint.
  std::vector<ModInt> fact, fact_inv, inv;
  Combinatorics(int val = 10000000) : val(val), fact(val + 1), fact_inv(val + 1), inv(val + 1) {
    fact[0] = 1;
    for (int i = 1; i <= val; ++i) fact[i] = fact[i - 1] * i;
    fact_inv[val] = ModInt(1) / fact[val];
    for (int i = val; i > 0; --i) fact_inv[i - 1] = fact_inv[i] * i;
    for (int i = 1; i <= val; ++i) inv[i] = fact[i - 1] * fact_inv[i];
  }
  ModInt nCk(int n, int k) const {
    if (n < 0 || n < k || k < 0) return 0;
    assert(n <= val && k <= val);
    return fact[n] * fact_inv[k] * fact_inv[n - k];
  }
  ModInt nPk(int n, int k) const {
    if (n < 0 || n < k || k < 0) return 0;
    assert(n <= val);
    return fact[n] * fact_inv[n - k];
  }
  ModInt nHk(int n, int k) const {
    if (n < 0 || k < 0) return 0;
    return k == 0 ? 1 : nCk(n + k - 1, k);
  }
};
using ModInt = MInt<MOD>;

template <typename T>
struct SegmentTree {
  using Monoid = typename T::Monoid;

  SegmentTree(int n) : SegmentTree(std::vector<Monoid>(n, T::unity())) {}

  SegmentTree(const std::vector<Monoid> &a) : n(a.size()) {
    while (p2 < n) p2 <<= 1;
    dat.assign(p2 << 1, T::unity());
    for (int i = 0; i < n; ++i) dat[i + p2] = a[i];
    for (int i = p2 - 1; i > 0; --i) dat[i] = T::merge(dat[i << 1], dat[(i << 1) + 1]);
  }

  void set(int idx, Monoid val) {
    idx += p2;
    dat[idx] = val;
    while (idx >>= 1) dat[idx] = T::merge(dat[idx << 1], dat[(idx << 1) + 1]);
  }

  Monoid get(int left, int right) const {
    Monoid l_res = T::unity(), r_res = T::unity();
    for (left += p2, right += p2; left < right; left >>= 1, right >>= 1) {
      if (left & 1) l_res = T::merge(l_res, dat[left++]);
      if (right & 1) r_res = T::merge(dat[--right], r_res);
    }
    return T::merge(l_res, r_res);
  }

  Monoid operator[](const int idx) const { return dat[idx + p2]; }

  template <typename G>
  int find_right(int left, G g) {
    if (left >= n) return n;
    Monoid val = T::unity();
    left += p2;
    do {
      while (!(left & 1)) left >>= 1;
      Monoid nx = T::merge(val, dat[left]);
      if (!g(nx)) {
        while (left < p2) {
          left <<= 1;
          nx = T::merge(val, dat[left]);
          if (g(nx)) {
            val = nx;
            ++left;
          }
        }
        return left - p2;
      }
      val = nx;
      ++left;
    } while (__builtin_popcount(left) > 1);
    return n;
  }

  template <typename G>
  int find_left(int right, G g) {
    if (right <= 0) return -1;
    Monoid val = T::unity();
    right += p2;
    do {
      --right;
      while (right > 1 && !(right & 1)) right >>= 1;
      Monoid nx = T::merge(dat[right], val);
      if (!g(nx)) {
        while (right < p2) {
          right = (right << 1) + 1;
          nx = T::merge(dat[right], val);
          if (g(nx)) {
            val = nx;
            --right;
          }
        }
        return right - p2;
      }
      val = nx;
    } while (__builtin_popcount(right) > 1);
    return -1;
  }

private:
  int n, p2 = 1;
  std::vector<Monoid> dat;
};

namespace monoid {
template <typename T>
struct RangeMinimumQuery {
  using Monoid = T;
  static constexpr T unity() { return std::numeric_limits<T>::max(); }
  static T merge(const T &a, const T &b) { return std::min(a, b); }
};

template <typename T>
struct RangeMaximumQuery {
  using Monoid = T;
  static constexpr T unity() { return std::numeric_limits<T>::min(); }
  static T merge(const T &a, const T &b) { return std::max(a, b); }
};

template <typename T>
struct RangeSumQuery {
  using Monoid = T;
  static constexpr T unity() { return 0; }
  static T merge(const T &a, const T &b) { return a + b; }
};
}  // monoid

int main() {
  constexpr int X = 2500;
  int n; cin >> n;
  vector<int> a(n); REP(i, n) cin >> a[i];
  vector<int> l(n, 1);
  vector<SegmentTree<monoid::RangeSumQuery<ModInt>>> col(X, n), row(n, X);
  col[a[n - 1] - a[n - 2]].set(n - 1, 1);
  row[n - 1].set(a[n - 1] - a[n - 2], 1);
  for (int i = n - 3; i >= 0; --i) {
    vector<ModInt> dp(X, 0);
    vector<int> r(X, n);
    int pos = 1;
    FOR(j, i + 2, n) {
      for (; pos < a[j] - a[i]; ++pos) r[pos] = j;
      dp[pos] += row[j].get(1, pos);
    }
    FOR(j, 1, X) dp[j] += col[j].get(i + 2, r[j]);
    FOR(j, 1, X) {
      if (dp[j] > 0) col[j].set(i + 1, dp[j]);
    }
    FOR(j, 1, X) {
      if (dp[j] > 0) row[i + 1].set(j, dp[j]);
    }
    // (i, i + 1)
    int diff = a[i + 1] - a[i];
    FOR(j, i + 2, n) {
      ModInt sum = 0;
      for (; l[j] < diff; ++l[j]) {
        ModInt val = row[j][l[j]];
        sum += val;
        if (val > 0) {
          row[j].set(l[j], 0);
          col[l[j]].set(j, 0);
        }
      }
      row[j].set(l[j], row[j][l[j]] + sum);
      col[l[j]].set(j, col[l[j]][j] + sum);
    }
  }
  ModInt ans = 0;
  FOR(i, 1, n) FOR(j, l[i], X) ans += row[i][j] * j;
  cout << ans * 2 << '\n';
  return 0;
}