import java.util.*

class ArrayWrapper<T>() {
    val contents = ArrayList<T>()

    fun add(item: T) {
        contents.add(item)
    }

    fun minus(): ArrayWrapper<T> {
        val result = ArrayWrapper<T>()
        result.contents.addAll(contents)
        var i = contents.size();
        for (a in contents) {
            result.contents[--i] = a;
        }
        return result
    }

    fun get(index: Int): T {
        return contents.get(index)
    }
}

fun box(): String {
    val v1 = ArrayWrapper<String>()
    v1.add("foo")
    v1.add("bar")
    val v2 = -v1
    return if (v2[0] == "bar" && v2[1] == "foo") "OK" else "fail"
}