import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

import sun.management.resources.agent_sv;

public class Main {

	public static void main(String[] args) {
	      BufferedReader stdReader =new BufferedReader(new InputStreamReader(System.in));
	      try {
		      int N = Integer.parseInt(stdReader.readLine());
		      int[] items = new int[11];
		      for(int i=0;i<N;i++){
		    	  String[] temps = stdReader.readLine().split(" ");
		    	  for(int j=0;j<temps.length;j++){
		    		  items[Integer.parseInt(temps[j])]++;
		    	  }
		      }
		      int ans = 0;
		      int sum = 0;
		      for(int i=1;i<=10;i++){
		    	  if(items[i] /2 > 0){
		    		  ans += items[i] /2;
		    		  items[i] %= 2;
		    	  }
		    	  sum += items[i];
		      }
		      
		      ans += sum /4;
		      System.out.println(ans);
	    	  } catch (IOException e) {
			e.printStackTrace();
	      }
	}	
}