#include <bits/stdc++.h>
using namespace std;
vector<pair<int, int> > sol;
long long ar[1005], DP[1005][1005], pre[1005][1005];
long long N, K;
void solve(int x) {
  for (int i = 0; i < N; i++)
    for (int j = 0; j <= K; j++) {
      DP[i][j] = 0;
      pre[i][j] = 0;
    }
  for (int i = 0; i < N; i++) DP[i][1] = 1;
  pre[0][1] = 1;
  int lft = 0;
  for (int i = 0; i < N; i++) {
    while (ar[i] - ar[lft] >= x && lft <= (i - 1)) lft++;
    lft--;
    if (ar[i] - ar[0] < x) {
      for (int j = 1; j <= K; j++) {
        pre[i][j] = (i == 0 ? 0 : pre[i - 1][j]) + DP[i][j];
        pre[i][j] %= 998244353;
      }
      continue;
    }
    for (int j = 1; j <= K; j++) {
      DP[i][j] += (pre[lft][j - 1]);
      DP[i][j] %= 998244353;
    }
    for (int j = 1; j <= K; j++) {
      pre[i][j] = (i == 0 ? 0 : pre[i - 1][j]) + DP[i][j];
      pre[i][j] %= 998244353;
    }
  }
}
int main() {
  cin >> N >> K;
  for (int i = 0; i < N; i++) cin >> ar[i];
  sort(ar, ar + N);
  long long ans = 0ll;
  for (int i = 1; i <= ((100000 / (K - 1)) + 5); i++) {
    solve(i);
    ans += pre[N - 1][K];
    ans %= 998244353;
  }
  cout << ans << endl;
  return (0);
}
