using System;
using System.IO;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
using System.Numerics;
using System.Diagnostics;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using static System.Math;
using static System.Console;


namespace yukicoder
{
    class Program
    {
        static void Main()
        {
            int n = int.Parse(Console.ReadLine());
            string chk = "12345678910";
            int[] num = new int[10];
            int cnt = 0;

            for (int i = 0; i < n; i++)
            {
                var nums = Console.ReadLine().Split().Select(int.Parse).ToArray();
                for (int j = 0; j < 3; j++)
                {
                    var s = nums[j] % 10;
                    num[s]++;

                    if (num[s] == 2)
                    {
                        cnt++;
                        num[s] = 0;
                    }
                }
            }

            cnt += (num.Sum() / 4);

            Console.WriteLine(cnt);

        }
    }
}