using System;
using System.Collections.Generic;
using System.IO;

namespace SockMerchant {
    class Program {
#if LOCAL_JUDGE
        private static readonly StreamWriter writer = new StreamWriter(@"..\..\output");
        private static readonly StreamReader reader = new StreamReader(@"..\..\input");
#else
        private static readonly StreamReader reader = new StreamReader(Console.OpenStandardInput(1024 * 10), System.Text.Encoding.ASCII, false, 1024 * 10);
        private static readonly StreamWriter writer = new StreamWriter(@System.Environment.GetEnvironmentVariable("OUTPUT_PATH"), true);
#endif

        static void Main(string[] args) {
            int n = Next();
            int[] a = new int[101];
            for(int i = 0; i < n; i++) {
                a[Next()]++;
            }
            int result = 0;
            for(int i = 0; i < 101; i++) {
                result += a[i] / 2;
            }
            writer.WriteLine(result);

            writer.Flush();
            writer.Close();
        }
        private static int Next() {
            int c;
            int res = 0;
            do {
                c = reader.Read();
                if(c == -1)
                    return res;
            } while(c != '-' && (c < '0' || c > '9'));
            int sign = 1;
            if(c == '-') {
                sign = -1;
                c = reader.Read();
            }
            res = c - '0';
            while(true) {
                c = reader.Read();
                if(c < '0' || c > '9')
                    return res * sign;
                res *= 10;
                res += c - '0';
            }
        }

        private static int[] ReadArray(int length) {
            int[] result = new int[length];
            for(int i = 0; i < length; i++) {
                result[i] = Next();
            }
            return result;
        }
    }
}