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

typedef long long ll;

int main(){
  int n,m;

  cin>>n>>m;
  vector<ll>vec(n);
  for(int i=0;i<n;i++){
    cin>>vec[i];
  }
  sort(vec.begin(),vec.end());

  ll sum=0;
  for(int i=0;i<m-1;i++){
    sum+=(vec[i+1]-vec[i])*(vec[i+1]-vec[i]);
  }

  ll minimum=sum;
  for(int i=0;i<n-m;i++){
    sum-=(vec[i+1]-vec[i])*(vec[i+1]-vec[i]);
    sum+=(vec[i+m-1]-vec[i+m])*(vec[i+m-1]-vec[i+m]);
    minimum=min(minimum,sum);
  }
  cout<<minimum<<endl;
  return(0);
}