/*
int      %o/%lo(八进制) %d/%i/%ld/%li(十进制) %x/%lx(十六进制)[如标名为o/lo/d/i/lo/li/x/lx即输出为八进制/十进制/十六进制]
longlong %lld
float    %f/%e
double   %lf/%le
char     %c
char[]   %s
'a'=97
'z'=122
'A'=65
'Z'=90
'0'=48
'9'=57
*/
#include <iostream>
#include <iomanip>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <ctime>
#include <limits>
#include <assert.h>
#include <stdlib.h>
using namespace std;
#define LL long long
#define ull unsigned long long
const int N=1e5+10;
const int INF=0x3f3f3f3f;
const double pi=3.1416;
int n,m,a[N],l,r,ans;
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<<endl;
return 0;
}