```fun main(args: Array<String>) { B().a...

# getting-started

[cypher121]

fun main(args: Array<String>) {
    B().apply {
        10.f()
    }
    
    A().apply {
        10.f()
    }
}

open class A {
    open fun Int.f() = println(this)
}

class B : A() {
    override fun Int.f() = println(4)
}

prints 4 and 10