#include<iostream>
#include<algorithm>
using namespace std;
int main(){
    int kuaiz,ke,ren=3,a[101];
    cin>>kuaiz>>ke;
    for(int i=1;i<=kuaiz;i++){
        cin>>a[i];;
    }
    ren+=ke;
    if(ren*2>kuaiz){
        cout<<"-1";
        return 0;
    }
    sort(a+1,a+kuaiz+1);
    int f[101][51]={0};
    bool pan[101][51]={0};
    for(int i=2;i<=kuaiz;i++){
        for(int j=1;j<=ren;j++){
            if(f[i-1][j]==0&&pan[i-1][j]==0){
                f[i][j]=f[i-2][j-1]+(a[i]-a[i-1])*(a[i]-a[i-1]);
                pan[i][j]=1;
            }else{
              f[i][j]= min (f[i-1][j],f[i-2][j-1]+(a[i]-a[i-1])*(a[i]-a[i-1]));
                pan[i][j]=1;
            }  
            //cout<<i<<" "<<j<<" "<<f[i][j]<<endl;   
            if(j==i/2){
                break;
            }       
        }
    }
    cout<<f[kuaiz][ren];
}