#include<bits/stdc++.h>
#define int long long
#define fo(i,a,b) for(int i=a;i<=b;i++)
using namespace std;
int n,k;
int a[10001];
int f[10001][1001];
main(){
	memset(f,0x3f,sizeof(f));
	cin>>n>>k;
	k+=3;
	if(k*2>n){
		cout<<-1;
		return 0;
	}
	fo(i,1,n) cin>>a[i];
	sort(a+1,a+n+1);
	fo(i,0,n) f[i][0]=0;
	fo(i,2,n){
		fo(j,1,k){
			f[i][j]=min(f[i-1][j],f[i-2][j-1]+(a[i]-a[i-1])*(a[i]-a[i-1]));
		}
	}
	cout<<f[n][k];
	return 0;
}