#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
  #define _GLIBCXX_DEBUG
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

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