using System;
using System.Collections.Generic;
using System.Linq;

public class Program
{
    public static void Main(string[] args)
    {
        var map = new Dictionary<int, int>();
        var n = int.Parse(Console.ReadLine());

        int[] items;
        for (var i=0; i<n; i++)
        {
            items = Console.ReadLine().Split(' ').Select(x => int.Parse(x)).ToArray();
            foreach (var data in items)
            {
                if (map.ContainsKey(data)) map[data]++;
                else map.Add(data, 1);
            }
        }
        var moreTwos = map.Values.Where(x => x >= 2).ToList();
        var ones = map.Values.Where(x => x == 1).ToList();
        int count = moreTwos.Sum() / 2 + ones.Sum() / 4;
        Console.WriteLine(count);
    }
}