#include<iostream>
#include<algorithm>
using namespace std;
 
const int N=1e5+10;
typedef long long LL;
LL x[N];
LL n,m;
 
bool check(int d)
{
	int pos=1;
	int cnt=1;
	while(cnt<m)
	{
		auto it=lower_bound(x+pos+1,x+1+n,x[pos]+d);
		if(it==x+1+n)return false;
		pos=it-x;
		cnt++;
	}
	return cnt>=m;
}
 
int main()
{
	cin>>n>>m;
	for(int i=1;i<=n;i++)cin>>x[i];
	sort(x+1,x+n+1);
 
	int l=0,r=x[n]-x[1];
	while(l<r)
	{
		int mid=(l+r+1)/2;
		if(check(mid))
		{
			l=mid;
		}
		else
		{
			r=mid-1;
		}
	}
 
	cout<<l<<endl;
 
	return 0;
}

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