#include<iostream>
#include<algorithm>
using namespace std;

int nlist[10];

int main(){
  int N,K;
  cin>>N>>K;
  for(int i=0;i<N;i++) cin>>nlist[i];
  double ans=-10.0;
  do{
    int div[10]={0};
    for(int i=0;i<K-1;i++) div[i]=1;
    do{
      double _max=0.0,_min=1e+9;
      double sum=nlist[0];
      int cnt=1;
      for(int i=0;i<N-1;i++){
	if(div[i]){
	  _max = max(sum/cnt,_max);
	  _min = min(sum/cnt,_min);
	  sum = 0.0;
	  cnt = 0;
	}
	sum += nlist[i+1];
	cnt++;
      }
      _max = max(sum/cnt,_max);
      _min = min(sum/cnt,_min);
      ans = max(ans,ceil(_max-_min));
    }while(next_permutation(div,div+N-1));
  }while(next_permutation(nlist,nlist+N));  
  cout<<ans<<endl;
  return 0;
}