#include <bits/stdc++.h>
using namespace std;
int n;
int k;
vector<int> v;
int dp[1003][1003];
int im[1003][1003];
int solve(int want) {
  for (int i = 0; i < n; i++) {
    for (int j = 0; j <= k; j++) {
      dp[i][j] = 0;
    }
  }
  for (int i = 0; i < n; i++) {
    for (int j = 0; j <= k; j++) {
      im[i][j] = 0;
    }
  }
  for (int i = 0; i < n; i++) {
    dp[i][1] = 1;
  }
  int ans = 0;
  for (int i = 0; i < n; i++) {
    int z = lower_bound(v.begin() + i + 1, v.end(), v[i] + want) - v.begin();
    for (int j = 0; j <= k; j++) {
      dp[i][j] += im[i][j];
      im[i + 1][j] += im[i][j];
      if (dp[i][j] >= 998244353) dp[i][j] -= 998244353;
      if (im[i + 1][j] >= 998244353) im[i + 1][j] -= 998244353;
      int go = v[i] + want;
      im[z][j + 1] += dp[i][j];
      if (im[z][j + 1] >= 998244353) im[z][j + 1] -= 998244353;
    }
    ans += dp[i][k];
    if (ans >= 998244353) ans -= 998244353;
  }
  return ans;
}
int main() {
  cin >> n >> k;
  for (int i = 0; i < n; i++) {
    int a;
    scanf("%d", &a);
    v.push_back(a);
  }
  sort(v.begin(), v.end());
  int num_interval = k - 1;
  int maxi = v.back() / num_interval;
  long long int ans = 0;
  for (int j = 1; j <= maxi; j++) {
    ans += solve(j);
  }
  ans %= 998244353;
  printf("%lld\n", ans);
  return 0;
}
