/*
    author: harvish
    lang : c++11
    url : hackerrank.com/challenges/angry-children
*/

#include<bits/stdc++.h>
using namespace std;
int main() {
	int n;
	int k;
	cin >> n >> k;
	long long int a[n];
	for(int i=0;i<n;i++) {
		cin >> a[i];
	}
	sort(a,a+n);
	long long int min_val=LLONG_MAX;

	for(int i=2;i<n;i++) {
		min_val = min(min_val,(a[i]-a[i-k+1]));
	}
	cout<< min_val << endl;

	return 0;
}