import java.io._
import java.math._
import java.security._
import java.text._
import scala.collection.mutable._
import java.util.concurrent._
import java.util.function._
import java.util.regex._
import java.util.stream._
object Solution {
def sockMerchant(n: Int, ar: Array[Int]): Int = {
var pairs: HashMap[Int,Int] = HashMap.empty[Int,Int]
var count = 0;
for (a <- ar){
if (pairs.contains(a)){
count += 1
pairs -= (a)
}else{
pairs += (a -> a)
}
}
return count
}
def main(args: Array[String]) {
val stdin = scala.io.StdIn
val printWriter = new PrintWriter(sys.env("OUTPUT_PATH"))
val n = stdin.readLine.trim.toInt
val ar = stdin.readLine.split(" ").map(_.trim.toInt)
val result = sockMerchant(n, ar)
printWriter.println(result)
printWriter.close()
}
}