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