package InterviewQuestions;
import java.util.*;
public class AggressiveCows {
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
int tc = sc.nextInt();
int[] arr = new int[n];
for(int i = 0; i< n; i++)
arr[i] = sc.nextInt();
Arrays.sort(arr);
System.out.println(binarySearch(arr, n,tc));
}
public static int binarySearch(int[] arr, int n, int tc) {
int lo = 1;
int hi = arr[n-1]-arr[0];
int mid = hi + (lo-hi)/2;
int ans = -1;
while(lo <= hi) {
if(isvalid(arr, mid, tc)) {
ans = mid;
lo = mid+ 1;
}
else {
hi = mid - 1;
}
}
return ans;
}
public static boolean isvalid(int[] arr, int mid, int tc) {
int cordinate = arr[0];
int nc = 1;
for(int i = 1; i < arr.length; i++) {
if(arr[i] - cordinate >= mid) {
nc++;
cordinate = arr[i];
if(nc == tc)
return true;
}
}
return false;
}
}