#include <bits/stdc++.h>
using namespace std;
const int maxn = 300000 + 5;
int a[maxn], dp[maxn];
int n, k;
bool ok_hack(int x) {
  memset(dp, 0, sizeof(dp));
  int last = 0;
  for (int i = k; i <= n; i++) {
    if (a[i] - a[dp[i - k] + 1] <= x) last = i;
    dp[i] = last;
  }
  return dp[n] == n;
}
int main() {
  scanf("%d%d", &n, &k);
  for (int i = 1; i <= n; i++) scanf("%d", &a[i]);
  sort(a + 1, a + n + 1);
  a[0] = 0;
  int l = 0, r = a[n] - a[1];
  while (l < r) {
    int mid = r + l >> 1;
    if (ok_hack(mid))
      r = mid;
    else
      l = mid + 1;
  }
  printf("%d\n", l);
  return 0;
}
