#include <iostream>
#include <cstring>
#include <algorithm>
#include <bits/stdc++.h>
#define ll long long
using namespace std;
bool yes(ll int a[],int n,int c,ll int mid){
ll int last = a[0];
int crr = 1;
for(int i=1;i<n;i++){
if(abs(a[i]-last)>=mid){
last = a[i];
crr++;
if(crr==c){
return true;
}
}
}
return false;
}
int main(){
int n,c;
cin >> n>> c;
ll int minn = INT_MAX,maxx = INT_MIN;
ll int a[n];
for(int i=0;i<n;i++){
cin >> a[i];
minn = min(minn,a[i]);
maxx = max(maxx,a[i]);
}
//cout<<minn<<" "<<maxx<<"\n";
ll int sta = minn,end = maxx-minn,ans = 0;
while(sta<=end){
ll int mid = (sta+end)/2;
if(yes(a,n,c,mid)){
ans = mid;
sta = mid+1;
}
else{
end = mid-1;
}
}
cout<<ans;
}
