import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
public class No29_2{

	public static void main(String[] args)  throws IOException{
		//パワーアップ　作り直し
		ArrayList<String> list = new ArrayList<>();
		int count = 0 , i;
		
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		
		int N = Integer.parseInt(br.readLine());
		for(i = 0;i < N;i++) {
			for(String str : br.readLine().split(" ")) {
				if(list.contains(str)) {
					count++;
					list.remove(str);
				}else {
					list.add(str);
				}
			}
		}

		br.close();
		
		count += (int)(list.size() / 4);
		System.out.println(count);
	}

}