#include <bits/stdc++.h>
using namespace std;
const int INF = 1 << 30;
const int MAXN = 1e3 + 5;
int arr[MAXN];
int dp[MAXN][MAXN], pref[MAXN][MAXN];
int le[MAXN];
const int MOD = 998244353;
int n, k;
int add(int a, int b) {
  a += b;
  while (a < 0) a += MOD;
  return a % MOD;
}
int mul(int a, int b) { return (long long)a * b % MOD; }
int solve(int x) {
  for (int i = 0; i <= k; i++) {
    for (int j = 0; j <= n; j++) {
      dp[i][j] = 0;
    }
  }
  le[0] = 0;
  for (int i = 1; i <= n; i++) {
    le[i] = le[i - 1];
    while (arr[i] - arr[le[i] + 1] >= x) le[i]++;
  }
  dp[0][0] = 1;
  for (int i = 0; i + 1 <= k; i++) {
    pref[i][0] = dp[i][0];
    for (int j = 1; j <= n; j++) {
      pref[i][j] = add(pref[i][j - 1], dp[i][j]);
    }
    for (int j = 1; j <= n; j++) {
      dp[i + 1][j] = pref[i][le[j]];
    }
  }
  int res = 0;
  for (int i = 1; i <= n; i++) res = add(res, dp[k][i]);
  return res;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cin >> n >> k;
  for (int i = 1; i <= n; ++i) {
    cin >> arr[i];
  }
  sort(arr + 1, arr + n + 1);
  int ans = 0;
  for (int i = 1; i <= arr[n] / (k - 1); ++i) {
    ans = add(ans, solve(i));
  }
  cout << ans << '\n';
  return 0;
}
