package Yukicoder

fun main(args: Array<String>) {
    fun readLineLongArray(): List<Long> {
        val str = readLine() as String
        val arrStr = str.split(" ")
        val ret = arrStr.map { it.toLong() }
        return ret
    }

    fun readLineLong(): Long {
        val str = readLine() as String
        return str.toLong()
    }

    fun readLineInt(): Int {
        val str = readLine() as String
        return str.toInt()
    }

    fun readLineIntArray() : List<Int> {
        val str = readLine() as String
        val arrStr = str.split(" ")
        val ret = arrStr.map { it.toInt() }
        return ret
    }

    fun readLineDoubleArray(): List<Double> {
        val str = readLine() as String
        val arrStr = str.split(" ")
        val ret = arrStr.map { it.toDouble() }
        return ret
    }

    fun readLineDouble() : Double {
        val str = readLine() as String
        return str.toDouble()
    }


//    fun readLineStringArray(): List<String> {
//        val str = readLine() as String
//        val arrStr = str.split(" ")
//        return arrStr
//    }

    val num = readLineInt()
    var arr = Array<Int>(10, {0})
    for (i in 1..num) {
        val input = readLineIntArray()
        for (item in input) {
            arr[(item-1)]++
        }
    }

    val ans = arr.map { it/2 }.sum() + arr.map { it%2 }.sum()/4
    println(ans)
}