import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
public class No29_3{

	public static void main(String[] args)  throws IOException{
		//パワーアップ　作り直し2回目
		int count = 0 , i;
		String[] text = readStr();
		ArrayList<String> al = new ArrayList<>();
		
		int N = Integer.parseInt(text[0]);
		for(i = 1;i <= N;i++) {
			for(String str : text[i].split(" ")) {
				if(al.contains(str)) {
					count++;
					al.remove(str);
				}else {
					al.add(str);
				}
			}
		}
		
		count += (int)(al.size() / 4);
		System.out.println(count);
	}

	public static String[] readStr() throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		ArrayList<String> list = new ArrayList<>();
		
		do {
			list.add(br.readLine());
		}while(br.ready());
		
		br.close();
		
		String[] text = new String[list.size()];
		list.toArray(text);
		
		return text;
		
	}
}