#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<int,int> P;
#define REP(i,n) for(ll i=0;i<ll(n);i++)

ll c[100010];

int main(void){
	cin.tie(nullptr);  ios_base::sync_with_stdio(false);
	ll i,j;

	ll N,M;
	cin >> N >> M;
	vector<ll> a(N);
	REP(i,N) cin >> a[i];

	sort(a.begin(),a.end());

	for(i=1;i<N;i++){
		c[i]=c[i-1]+(a[i]-a[i-1])*(a[i]-a[i-1]);
	}

	ll mn=1e18;
	for(i=0;i<N;i++){
		if(i+M-1<N){
			mn=min(mn,c[i+M-1]-c[i]);
		}
	}


	cout << mn << endl;



	return 0;
}