#include <bits/stdc++.h>
using namespace std;
#define int long long
int n,h;
const int N = 1e6+10;
int a[N];	
bool check(int x) {
	int cnt=0,pre=-1;
	for(int i=1;i<=n;i++) {
		if(pre==-1) {
			pre=a[i];
			cnt++;
		}
		else if(a[i]-pre>=x) {
			pre=a[i];
			cnt++;
		}
		if(cnt>=h) return true;
	}
	return false;
}
signed main(){
	cin>>n>>h;
	for(int i=1;i<=n;i++) cin>>a[i];
	sort(a+1,a+n+1);
	int l=0,r=1e9,ans;
	while(l<=r) {
		int mid=l+r>>1;
		if(check(mid)) {
			ans=mid;
			l=mid+1;
		}
		else r=mid-1;
	}
	cout<<ans<<endl;
}