public class Recursion
{

public static void main(String[] args)
{
    f(3);

}

public static void f(int x)
{
    if(x>0)
    {
        System.out.println(x + "top");
        f(x-1);
        System.out.println(x + "bottom");
        f(x-1);
    }
    System.out.println("bert");
}
}