#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using ll = long long;
#define rep(i,n) for(int i=0;i<(int)(n);i++)
using mint = atcoder::modint998244353;

int main(){
	int n,m;
	cin>>n>>m;
	vector<ll> a(n);
	rep(i,n) cin>>a.at(i);
	sort(a.begin(),a.end());
	vector<ll> b(n-1);
	rep(i,n-1) b.at(i)=(a.at(i+1)-a.at(i))*(a.at(i+1)-a.at(i));
	vector<ll> c(n,0);
	rep(i,n-1) c.at(i+1)=c.at(i)+b.at(i);
	ll ans=1e18;
	rep(i,n-m+1){
		ans=min(ans,c.at(i+m-1)-c.at(i));
	}
	cout<<ans<<endl;
}