using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine($"[7,1,5,3,6,4] = {SellAndBuy([7,1,5,3,6,4])} = Expect[5]");

        Console.WriteLine($"[7,1,5,3,6,4,10] = {SellAndBuy([7,1,5,3,6,4,10])} = Expect[9]");

        Console.WriteLine($"[7,1,15,3,6,4,10] = {SellAndBuy([7,1,15,3,6,4,10])} = Expect[14]");

        Console.WriteLine($"[] = {SellAndBuy([])} = Expect[0]");

        Console.WriteLine($"[1] = {SellAndBuy([1])} = Expect[0]");

        Console.WriteLine($"[2,1] = {SellAndBuy([2,1])} = Expect[0]");

        Console.WriteLine($"[2,10] = {SellAndBuy([2,10])} = Expect[8]");

    }

    private static int  SellAndBuy(int[] array)

    {

        if (array.Length < 2)

        {

            return 0;

        }

        var res = 0;

        var l = array.Length;

        for(var left = 0; left < l - 1; left++)

        {

            for(var right = left; right < l; right++)

            {

                res = int.Max(res, array[right] - array[left]);

            }

        }

        return res;

    }

}