#include<bits/stdc++.h>
using namespace std;
int a[100001];
int n,m;
bool search(int dis)
{
	int ans=1;int pre=1;
	while(ans<m)
	{
		int low=lower_bound(a+1,a+1+n,a[pre]+dis)-a;
		if(low>=n+1)
		{
			if(ans<m)
			return false;
			else if(ans>=m) 
			return true;
		}
		else if(low<=n)
		{
			ans++;
			pre=low;
		}
	}
	return true;
}
int main()
{
	cin>>n>>m;
	for(int i=1;i<=n;i++)
	{
		cin>>a[i];
	}
	sort(a+1,a+1+n);
	int pre;int left=1;int right=a[n];
	while(left+1<right)
	{
		int mid=(left+right)/2;
		bool p=search(mid);
		if(p==false)
		{
			right=mid;
		}
		else
		left=mid;
	}
	cout<<left;
	return 0;
}