#include <bits/stdc++.h>
#include<cstring>
using namespace std;

int n,c; 
int a[100001];

bool ss(int ma)
{
	int cnt = 1;
	int l = a[0];
	for(int i = 1;i < n; i ++)
	{
		if(a[i] - l < ma) continue;
		cnt ++;
		l = a[i];
	}
	if(cnt >= c) return true;
	return false;
}

int main(){
	cin >> n >> c;
	for(int i = 0;i < n;i ++)
	{
		cin >> a[i];
	}
	sort(a,a+n);
	int l = 1,r = n - 1;
    while (r- l > 1)
    {
        int mid = (l +r) / 2;
        if(ss(mid))	l = mid;
		else r = mid; 
    }
    if(ss(r)) cout << r;
    else cout<< l;
	return 0;
}