#include <bits/stdc++.h>
using namespace std;
const int maxn = 1000 + 10;
const int MOD = 998244353;
const int DEBUG = 0;
inline int inc(int a, int b) {
  return (a + b >= MOD) ? (a + b - MOD) : (a + b);
}
inline int dec(int a, int b) { return (a >= b) ? (a - b) : (a + MOD - b); }
inline int mul(int a, int b) { return 1LL * a * b % MOD; }
inline int power(int x, int k) {
  int tmp = 1;
  while (k) {
    if (k & 1) tmp = mul(tmp, x);
    x = mul(x, x);
    k >>= 1;
  }
  return tmp;
}
int n, k, Ans, a[maxn], dp[maxn][maxn], sum[maxn][maxn];
inline void solve(int x) {
  for (int i = 0; i <= k; i++) {
    for (int j = 0; j <= n; j++) dp[i][j] = sum[i][j] = 0;
  }
  for (int i = 1; i <= n; i++) dp[1][i] = 1;
  for (int i = 1; i <= n; i++) sum[1][i] = inc(sum[1][i - 1], dp[1][i]);
  for (int i = 2; i <= k; i++) {
    sum[i][0] = 0;
    int l = 1;
    for (int j = 1; j <= n; j++) {
      while (a[l] <= a[j] - x) l++;
      dp[i][j] = sum[i - 1][l - 1];
      sum[i][j] = inc(sum[i][j - 1], dp[i][j]);
    }
  }
  int now = 0;
  for (int i = 1; i <= n; i++) now = inc(now, dp[k][i]);
  Ans = inc(Ans, now);
  if (DEBUG) printf("%d %d\n", x, now);
}
int main() {
  scanf("%d%d", &n, &k);
  for (int i = 1; i <= n; i++) scanf("%d", &a[i]);
  sort(a + 1, a + n + 1);
  Ans = 0;
  for (int i = 1; i <= a[n] / (k - 1); i++) {
    solve(i);
  }
  printf("%d\n", Ans);
  return 0;
}
