/* -*- coding: utf-8 -*-
 *
 * 2548.cc:  No.2548 Problem Selection - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_N = 100000;
const long long LINF = 1LL << 62;

/* typedef */

typedef long long ll;

/* global variables */

int as[MAX_N];
ll dds[MAX_N], ddss[MAX_N];

/* subroutines */

/* main */

int main() {
  int n, m;
  scanf("%d%d", &n, &m);
  for (int i = 0; i < n; i++) scanf("%d", as + i);
  sort(as, as + n);

  for (int i = 0; i + 1 < n; i++) {
    int d = as[i + 1] - as[i];
    dds[i] = (ll)d * d;
    ddss[i + 1] = ddss[i] + dds[i];
  }

  ll mins = LINF;
  for (int i = 0; i + m - 1 < n; i++)
    mins = min(mins, ddss[i + m - 1] - ddss[i]);

  printf("%lld\n", mins);

  return 0;
}