#include <bits/stdc++.h>
using namespace std;
int const N = 1000, M = 100000, md = 998244353;
int x[N + 1], dp[N + 1][2], pr[N + 1][2];
inline void ad(int &x, int y) {
  if ((x += y) >= md) x -= md;
}
int main() {
  int n, k;
  scanf("%d%d", &n, &k);
  for (int i = 1; i < (int)(n + 1); ++i) scanf("%d", x + i);
  sort(x + 1, x + n + 1);
  int an = 0;
  for (int i = 1; i < (int)(M / (k - 1) + 1); ++i) {
    for (int j = 0; j < (int)(n + 1); ++j)
      for (int w = 0; w < (int)(2); ++w) dp[j][w] = 0;
    dp[0][0] = 1;
    for (int j = 0; j < (int)(k); ++j) {
      int a = 0, b = 0;
      pr[0][0] = j == 0;
      for (int w = 1; w < (int)(n + 1); ++w) {
        for (int z = 0; z < (int)(2); ++z)
          ad(pr[w][z] = pr[w - 1][z], dp[w][z]);
        while (a < w && x[w] - x[a + 1] > i) ++a;
        while (b < w && x[w] - x[b + 1] >= i) ++b;
        for (int z = 0; z < (int)(2); ++z) dp[w][z] = 0;
        for (int z = 0; z < (int)(2); ++z) ad(dp[w][z], pr[a][z]);
        if (a != b)
          for (int z = 0; z < (int)(2); ++z) {
            ad(dp[w][1], pr[b][z]);
            ad(dp[w][1], md - pr[a][z]);
          }
      }
    }
    for (int j = 2; j < (int)(n + 1); ++j) ad(an, (long long)dp[j][1] * i % md);
  }
  printf("%d\n", an);
}
