using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;

namespace yukicore
{
    internal class Program
    {
        //29
        private static void Main(string[] args)
        {
            IEnumerable<int> gets = new int[3];
            int[] items = new int[10];
            Console.ReadLine();
            int ans = 0;
            while (true)
            {
                var tmp = Console.ReadLine();
                if (string.IsNullOrEmpty(tmp)) break;
                gets = tmp.Split(' ')
                    .Select(x => x.Length == 2 ? 9 : x[0] - 49);
                foreach (var get in gets)
                {
                    items[get]++;
                }
            }
           ans= items.Select(x => x / 2).Sum() + items.Select(x => x % 2).Sum() / 4;
            Console.WriteLine(ans);
        }
    }
}