class Program
{
    static void Main(string[] args)
    {
        string inputCount = Console.ReadLine()!;
        int count = int.Parse(inputCount);
        List<int> numList = new List<int>();

        for (int i = 0; i < count; i++)
        {
            string[] inputItem = Console.ReadLine()!.Split(' ');
            for (int j = 0; j < inputItem.Length; j++)
            {
                numList.Add(int.Parse(inputItem[j]));
            }
        }

        int ans = 0;
        numList.Sort();
        int judg = 0;
        for (int i = 1; i < numList.Count; i++)
        {
            if (numList[i] == numList[i - 1] && numList[i] != judg)
            {
                judg = numList[i];
                ans++;
            }
            else
            {
                judg = 0;
            }
        }

        int num = numList.Count - ans * 2;
        num = num / 4;

        Console.WriteLine(ans + num);
    }
}