using System;
using System.Linq;
using System.Collections.Generic;

class AOJ {
    static void Main() {
        int n = int.Parse(Console.ReadLine());
        int[] items = new int[11];
        for (int i = 0; i < n; i++) {
            int[] acquired_items = Console.ReadLine().Split().Select(int.Parse).ToArray();
            foreach (var elem in acquired_items) {
                items[elem]++;
            }
        }
        int cnt = 0;
        while (true) {
            bool power_up = false;
            for (int i = 1; i <= 10; i++) {
                if(items[i] >= 2) {
                    cnt++;
                    items[i] -= 2;
                    power_up = true;
                }
            }
            if (power_up == false) {
                break;
            }
        }
        while (true) {
            bool power_up = false;
            List<int> tmp = new List<int>();
            for (int i = 1; i <= 10; i++) {
                if(items[i] != 0) {
                    tmp.Add(i);
                }
            }
            if(tmp.Count >= 4) {
                cnt++;
                for (int i = 0; i < 4; i++) {
                    items[tmp[i]]--;
                }
                power_up = true;
            }
            if (power_up == false) {
                break;
            }
        }
        Console.WriteLine(cnt);
    }
}