using System;

public class Program

{

    public static void Main()

    {

        new Program();

    }

    private Program()

    {

        int[] arr = { 1, 2, 1, 2, 1 };

        int k = 2;

        Array.Sort(arr);

        int minUnfairness = int.MaxValue;

        for (int i = 0; i < arr.Length - k - 1; i++)

        {

            // a sliding window of length k

            int currUnfairness = GetUnfairness(arr[i], arr[i + k - 1]);

            if (minUnfairness > currUnfairness)

            {

                minUnfairness = currUnfairness;

            }

        }

        Console.WriteLine("Min unfairness is " + minUnfairness);

    }

    private int GetUnfairness(int a, int b)

    {

        return Math.Max(a, b) - Math.Min(a, b);

    }

}