using System;
using System.Linq;

class Program
{
    static void Main()
    {
        int N = int.Parse(Console.ReadLine());
        var A = Array.ConvertAll(Console.ReadLine().Split(), int.Parse);

        int[] freq = new int[N + 1];

        foreach (var x in A) freq[x]++;

        long ans = 0;
        foreach (var f in freq) ans += f / 2;

        Console.WriteLine(ans);
    }
}