public static void main(String[] args) {
        try (var br = new BufferedReader(new InputStreamReader(System.in));
             var bw = new BufferedWriter(new OutputStreamWriter(System.out))) {
            int n = Integer.parseInt(br.readLine().trim());
            String[] socks = br.readLine().trim().split(" ");
            int[] sockCounts = new int[101];
            for (String sock : socks) {
                int color = Integer.parseInt(sock);
                sockCounts[color]++;
            }
            int pairs = 0;
            for (int count : sockCounts) {
                pairs += count >> 1;
            }
            bw.write(String.valueOf(pairs));
            bw.newLine();
            bw.flush();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }