using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (n, m) = (c[0], c[1]);
        var a = NList;
        Array.Sort(a);
        var d2 = new long[n];
        for (var i = 1; i < n; ++i) d2[i] = d2[i - 1] + (long)(a[i] - a[i - 1]) * (a[i] - a[i - 1]);
        var ans = long.MaxValue;
        for (var i = 0; i < n; ++i) if (i + m - 1 < n) ans = Math.Min(ans, d2[i + m - 1] - d2[i]);
        WriteLine(ans);
    }
}