import java.util.*

fun main(args: Array<String>) {
    val count = readLine()!!.toInt()
    var items = mutableListOf<Int>()
    (1..count).forEach { items.addAll(readLine()!!.split(" ").map { it.toInt() }) }
    var ans = 0
    while (items.size >= 2) {
        items.sortWith(kotlin.Comparator { a, b -> comp(a,b,items) })
        val (a,b) = items.take(2)
        if(a == b) {
            ans++
            (0..1).forEach { items.removeAt(0) }
        } else if(items.size >= 4) {
            ans = ans + items.size / 4
            break
        } else {
            break
        }
    }
    println(ans)
}
fun comp(a:Int, b:Int, list : List<Int>):Int {
    val num1 = list.count { it == a }
    val num2 = list.count { it == b }
    if(num1 == num2) {
        return a.compareTo(b)
    }
    return num2.compareTo(num1)
}