#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
using namespace std;
int main() {
  cin.tie(0); cout.tie(0);
  ios::sync_with_stdio(false);
  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<long long> B(N - 1), C(N);
  for(int i = 0; i < N - 1; i++) {
    B[i] = (long long) (A[i + 1] - A[i]) * (A[i + 1] - A[i]);
    C[i + 1] = C[i] + B[i];
  }
  long long ans = 4000000000000000000;
  for(int i = 0; i + M - 1 < N; i++) {
    ans = min(ans, C[i + M - 1] - C[i]);
  }
  cout << ans << '\n';
  return 0;
}