#include <bits/stdc++.h>
using namespace std;
const int n0 = 1003, m = 1e5, mod = 998244353;
int n, k, a[n0], dp[2][n0], b[n0];
int calc(int gap) {
  for (int i = 1; i <= n; i++)
    b[i] = upper_bound(a + 1, a + n + 1, a[i] - gap) - a - 1;
  memset(&dp, 0, sizeof(dp));
  for (int j = 0; j <= n; j++) dp[0][j] = 1;
  for (int i = 1; i <= k; i++) {
    dp[i & 1][0] = 0;
    for (int j = 1; j <= n; j++) {
      int &x = dp[i & 1][j];
      x = dp[i & 1][j - 1] + dp[(i - 1) & 1][b[j]];
      x = (x >= mod) ? (x - mod) : x;
    }
  }
  return dp[k & 1][n];
}
int main() {
  ios_base::sync_with_stdio(0), cin.tie(0);
  cin >> n >> k;
  for (int i = 1; i <= n; i++) cin >> a[i];
  sort(a + 1, a + n + 1);
  int res = 0;
  for (int gap = 1; gap <= m / (k - 1); gap++) {
    res += calc(gap);
    if (res >= mod) res -= mod;
  }
  cout << res;
}
