import java.util.ArrayList

trait Tr {
   fun extra() : String = "_"
}

class N() : ArrayList<Any>(), Tr {
    override fun add(el: Any)  : Boolean {
        super<ArrayList>.add(el)
        return super<ArrayList>.add(el.toString() + super<Tr>.extra() + el + extra())
    }

   override fun extra() : String = super<Tr>.extra() + super<Tr>.extra()
}

fun box(): String {
    val n = N()
    n.add("239")
    if (n.get(0) == "239" && n.get(1) == "239_239__") return "OK";
    return "fail";
}