How to return one of two strings in Kotlin

So I just recently started learning Kotlin through Google's new course and I learn how to randomly choose a number from a dice. I'm slightly confused on part of it so I tried to make a random coin flip program to help understand it better. I try to use the .random to choose between the two strings but it doesn't work and gives a long error. Here's the code so far:

fun main() {
val coinSide = Coin()   
    println("You flipped a ${coinSide}")
​
​
}
​
class Coin (){
    
    fun flip() : String {
        val head = ("Heads")
        val tails = ("Tails")
        return (head..tails).random()
    }    
}