#include<bits/stdc++.h>
using namespace std;
const int N = 1e5+10;
int n,m,l,r,a[N],ans;
bool v[10005];
bool check(int mid){
	int sum = 1;
	int last = a[1];
	for(int i = 2;i <= n;i++){
		if(last + mid<=a[i]){
			last = a[i];
			sum++;
		}
	}
	return sum >= m;
}
int main(){
	cin >> n >> m;
	for(int i = 1;i <= n;i++)
	    cin >> a[i];
	sort(a+1,a+n+1);
	l = 1;
	r = a[n] - a[1];
	while(l<=r){
		int mid = (l+r)>>1;
		if(check(mid)){
			ans = mid;
			l = mid+1;
		}
		else
		    r = mid - 1;
	}
	cout << ans;
	return 0;
}