ll@n,@m,@a[n],s=0,z=m>1?ll_inf:0;
sortA(n,a);
rep(i,n-1){
	s+=(a[i+1]-a[i])**2;
	if(i>m-3){
		z<?=s;
		s-=(a[i-m+3]-a[i-m+2])**2;
	}
}
wt(z);