```#include <bits/stdc++.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;
}