public static void Main(string[] args)
{
Pilha p = new Pilha();
Console.WriteLine(p.empty());
Console.WriteLine(p.top());
p.push(10);
p.push(20);
p.push(30);
p.push(40);
p.lt();
Console.WriteLine("\n");
Console.WriteLine(p.top());
Console.WriteLine("\n");
p.pop();
Console.WriteLine("\n");
Console.WriteLine(p.top());
Console.WriteLine("\n");
p.pop(2);
Console.WriteLine(p.top());
Console.WriteLine("\n");
p.pop(2);
Console.WriteLine(p.top());
}