using System.Collections;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

internal class Program
{
    private const long mod = 998244353;
    private const long mod17 = 1000000007;
    private const long INF = mod17 * mod17;
    
    public static void Main(string[] args)
    {
        var line = getar();
        int n = line[0], m = line[1];
        var a = getar();
        Array.Sort(a);
        List<long> rd = mkar(n, (long)0);
        for (int i = 0; i + 1 < n; i++)
        {
            long dif = a[i + 1] - a[i];
            rd[i + 1] = rd[i] + dif * dif;
        }

        long ans = INF;
        for (int i = 0; i < n - (m - 1); i++)
        {
            long val = rd[i + m - 1] - rd[i];
            ans = Math.Min(ans, val);
        }
        Console.WriteLine(ans);
    }
    public class lower_bound<T> : IComparer<T> where T : IComparable<T>
    {
        public int Compare(T x, T y)
        {
            return 0 <= x.CompareTo(y) ? 1 : -1;
        }
    }
    public static List<T> mkar<T>(int n, T val)
    {
        List<T> res = new List<T>(n);
        for(int i=0;i<n;i++)res.Add(val);
        return res;
    }

    public static int[] getar()
    {
        var res = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
        return res;
    }
}