using System;
using System.Linq;

namespace Yukicoder
{
    class Program
    {
        static void Main(string[] args)
        {
            int N = int.Parse(Console.ReadLine());
            int[] list = new int[10];

            for (int i = 0; i < N; i++)
            {
                var data = Console.ReadLine().Split(' ').Select(x => int.Parse(x)).ToArray();
                foreach (var d in data)
                {
                    list[d - 1]++;
                }
            }

            int powerup = 0;
            int subPowerup = 0;
            foreach(var l in list)
            {
                powerup += l / 2;
                if (l % 2 == 1)
                    subPowerup++;
            }
            Console.WriteLine(powerup + (subPowerup / 4));
        }
    }
}