#include<iostream>
#include<vector>
#include<numeric>
#include<algorithm>
using namespace std;
#define int long long
signed main(){
	int N,M;
	cin >> N >> M;
	vector<int> a(N);
	for(int i = 0;i < N;i++) cin >> a[i];
	sort(a.begin(),a.end());
	vector<int> b(N - 1);
	for(int i = 0;i < N - 1;i++){
	b[i] = a[i + 1]  - a[i];
	b[i] = b[i] * b[i];
	
	}
	if(M == 1){
		cout << 0;
		return 0;
	}
	for(int i = 1;i < N - 1;i++)b[i] += b[i - 1];
	int ans = b[M - 2];
	for(int i = M - 1;i < N - 1;i++){
	ans = min(ans,b[i] - b[i - M + 1]);
	}
	cout << ans << endl;
}