Finding the number of pairs in an integer Array

This function returns the number of pairs of the same elements in the array

It takes, array length and the array as the parameter

n: Length of array

ar: Array of integers for example

4 6 7 8 7 6 6 7 6 4

returns 4

fun getNumberOfPairs(n: Int, ar: Array<Int>): Int {     val enteries = HashSet<Int>()     var pairs = 0      for (i in 0 until n) {         if (!enteries.contains(ar[i])) {             enteries.add(ar[i])         } else {             pairs++             enteries.remove(ar[i])         }     }      println(pairs)     return pairs } 

How can we write this code in a better way for readability|performance?

Thanks