#include <bits/stdc++.h>
using namespace std;
const int MOD = 998244353;
template <typename T>
struct modular {
  constexpr modular() : val(0) {}
  constexpr modular(const modular<T>& _m) : val(_m.val) {}
  template <typename U>
  constexpr modular(const U& _r = U()) {
    val = -MOD <= _r && _r < MOD ? _r : _r % MOD;
    if (val < 0) {
      val += MOD;
    }
  }
  const T operator()() { return val; }
  template <typename U>
  explicit operator U() const {
    return static_cast<U>(val);
  }
  modular<T>& operator+=(const modular<T>& _m) {
    if ((val += _m.val) >= MOD) {
      val -= MOD;
    }
    return *this;
  }
  modular<T>& operator-=(const modular<T>& _m) {
    if ((val -= _m.val) < 0) {
      val += MOD;
    }
    return *this;
  }
  modular<T>& operator*=(const modular<T>& _m) {
    val = modular<T>(static_cast<int64_t>(val) * static_cast<int64_t>(_m.val))
              .val;
    return *this;
  }
  modular<T>& operator/=(const modular<T>& _m) {
    T a = _m.val, b = MOD, u = 0, v = 1;
    while (a != 0) {
      T q = b / a;
      b -= q * a;
      swap(a, b);
      u -= q * v;
      swap(u, v);
    }
    return *this *= u;
  }
  modular<T>& operator=(const modular<T>& _m) {
    val = _m.val;
    return *this;
  }
  template <typename U>
  modular<T>& operator+=(const U& _r) {
    return *this += modular<T>(_r);
  }
  template <typename U>
  modular<T>& operator-=(const U& _r) {
    return *this -= modular<T>(_r);
  }
  template <typename U>
  modular<T>& operator*=(const U& _r) {
    return *this *= modular<T>(_r);
  }
  template <typename U>
  modular<T>& operator/=(const U& _r) {
    return *this /= modular<T>(_r);
  }
  template <typename U>
  modular<T>& operator=(const U& _r) {
    val = modular<T>(_r).val;
    return *this;
  }
  modular<T> operator-() { return modular<T>(-val); }
  template <typename U>
  friend bool operator==(const modular<U>&, const modular<U>&);
  friend std::istream& operator>>(std::istream& os, modular<T>& _m) {
    os >> _m.val;
    _m *= 1;
    return os;
  }
  friend std::ostream& operator<<(std::ostream& os, const modular<T>& _m) {
    return os << _m.val;
  }
  template <typename U>
  modular<T> exp(U e) {
    modular<T> res = 1;
    modular<T> b = val;
    if (e < 0) {
      b = 1 / b;
      e *= -1;
    }
    for (; e; e >>= 1) {
      if (e & 1) {
        res *= b;
      }
      b *= b;
    }
    return res;
  }

 private:
  T val;
};
template <typename T>
inline modular<T> operator+(const modular<T>& _lhs, const modular<T>& _rhs) {
  return modular<T>(_lhs) += _rhs;
}
template <typename T, typename U>
inline modular<T> operator+(const modular<T>& _lhs, const U& _rhs) {
  return modular<T>(_lhs) += _rhs;
}
template <typename T, typename U>
inline modular<T> operator+(const U& _lhs, const modular<T>& _rhs) {
  return modular<T>(_lhs) += _rhs;
}
template <typename T>
inline modular<T> operator-(const modular<T>& _lhs, const modular<T>& _rhs) {
  return modular<T>(_lhs) -= _rhs;
}
template <typename T, typename U>
inline modular<T> operator-(const modular<T>& _lhs, const U& _rhs) {
  return modular<T>(_lhs) -= _rhs;
}
template <typename T, typename U>
inline modular<T> operator-(const U& _lhs, const modular<T>& _rhs) {
  return modular<T>(_lhs) -= _rhs;
}
template <typename T>
inline modular<T> operator*(const modular<T>& _lhs, const modular<T>& _rhs) {
  return modular<T>(_lhs) *= _rhs;
}
template <typename T, typename U>
inline modular<T> operator*(const modular<T>& _lhs, const U& _rhs) {
  return modular<T>(_lhs) *= _rhs;
}
template <typename T, typename U>
inline modular<T> operator*(const U& _lhs, const modular<T>& _rhs) {
  return modular<T>(_lhs) *= _rhs;
}
template <typename T>
inline modular<T> operator/(const modular<T>& _lhs, const modular<T>& _rhs) {
  return modular<T>(_lhs) /= _rhs;
}
template <typename T, typename U>
inline modular<T> operator/(const modular<T>& _lhs, const U& _rhs) {
  return modular<T>(_lhs) /= _rhs;
}
template <typename T, typename U>
inline modular<T> operator/(const U& _lhs, const modular<T>& _rhs) {
  return modular<T>(_lhs) /= _rhs;
}
template <typename T>
inline bool operator==(const modular<T>& _lhs, const modular<T>& _rhs) {
  return _lhs.val == _rhs.val;
}
template <typename T, typename U>
inline bool operator==(const modular<T>& _lhs, const U& _rhs) {
  return _lhs == modular<T>(_rhs);
}
template <typename T, typename U>
inline bool operator==(const U& _lhs, const modular<T>& _rhs) {
  return modular<T>(_lhs) == _rhs;
}
template <typename T>
inline bool operator!=(const modular<T>& _lhs, const modular<T>& _rhs) {
  return !(_lhs == _rhs);
}
template <typename T, typename U>
inline bool operator!=(const modular<T>& _lhs, const U& _rhs) {
  return !(_lhs == _rhs);
}
template <typename T, typename U>
inline bool operator!=(const U& _lhs, const modular<T>& _rhs) {
  return !(_lhs == _rhs);
}
modular<int> dp[1024][1024];
void solve() {
  int n, k;
  cin >> n >> k;
  vector<int> a(n + 1);
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
  }
  sort(a.begin() + 1, a.end());
  int lim = a[n] / (k - 1);
  modular<int> res = 0;
  for (int x = 1; x <= lim; x++) {
    for (int i = 1; i <= n; i++) {
      dp[1][i] = i;
    }
    for (int len = 2; len <= k; len++) {
      for (int i = 1; i <= n; i++) {
        dp[len][i] = 0;
      }
    }
    for (int len = 1; len < k; len++) {
      int i = 1, j = 2;
      while (j <= n && a[j] - a[i] < x) {
        j++;
      }
      for (; j <= n; j++) {
        while (i + 1 < j && a[j] - a[i + 1] >= x) {
          i++;
        }
        dp[len + 1][j] = dp[len + 1][j - 1] + dp[len][i];
      }
    }
    res += dp[k][n];
  }
  cout << res;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  solve();
  cout << endl;
}
