using static System.Math;
using System;

public class Hello
{
    static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var n = int.Parse(line[0]);
        var k = int.Parse(line[1]);
        line = Console.ReadLine().Trim().Split(' ');
        var a = Array.ConvertAll(line, long.Parse);
        getAns(n, k, a);
    }
    static void getAns(int n, int k, long[] a)
    {
        Array.Sort(a);
        var b = new long[n - 1];
        for (int i = 0; i < n - 1; i++)
        {
            var t = a[i + 1] - a[i];
            b[i] = t * t;
        }
        var c = new long[n];
        c[0] = 0;
        for (int i = 1; i < n; i++) c[i] = c[i - 1] + b[i - 1];
        var ans = long.MaxValue;
        for (int i = k - 1; i < n; i++) ans = Min(ans, c[i] - c[i - k + 1]);
        Console.WriteLine(ans);
    }
}