#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N =1e6+5;
int n, m, a[N];
bool check(int x){
	int st = a[0];
	int cou = 1;
	for(int i = 1; i < n; i++){
		if(a[i] - st < x) continue;
		st = a[i];
		cou++;
	}
	return cou >= m;
}
void solve() {
	cin >> n >> m;
	for(int i = 0; i < n; i++){
		cin >> a[i];
	}
	sort(a, a+n);
	int l = 0, r = 1e9;
	int mid;
	while(l < r){
		mid = l + r + 1 >> 1;
		if(check(mid)) l = mid;
		else r = mid-1;
	}
	cout << l;
}

int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);

	int t = 1;
//	cin >> t;
	while (t--) {
		solve();
	}


	return 0;
}
/*
12 8
1
3
6
11
18
27
38
41
56
73
92
113

*/