#include <bits/stdc++.h>
using namespace std;

int main() {
  int N, M; cin >> N >> M;
  long long Ans = 1e18, Sum = 0;
  vector<long long> A(N); for (long long &B : A) cin >> B;
  sort(A.begin(), A.end());

  for (int i = 0; i < M - 1; i++)
    Sum += (A.at(i + 1) - A.at(i)) * (A.at(i + 1) - A.at(i));
  Ans = min(Ans, Sum);

  for (int i = M - 1; i < N - 1; i++) {
    Sum -= (A.at(i - M + 2) - A.at(i - M + 1)) * (A.at(i - M + 2) - A.at(i - M + 1));
    Sum += (A.at(i + 1) - A.at(i)) * (A.at(i + 1) - A.at(i));
    Ans = min(Ans, Sum);
  }

  cout << Ans << endl;
}