static void Main(string[] args)
{
var tree = new BinarySearchTree();
tree.Add(100, 20, 500, 10, 30, 40);
Console.WriteLine("InOrder:");
tree.InOrder(x => { Console.Write($"{x}, "); });
Console.WriteLine("\nPreOrder:");
tree.PreOrder(x => { Console.Write($"{x}, "); });
Console.WriteLine("\nPostOrder:");
tree.PostOrder(x => { Console.Write($"{x}, "); });
}