import java.util.*;

class Yuki29{
	public static void main(String[] args){
		Scanner stdIn = new Scanner(System.in);

		int n = stdIn.nextInt();
		int[] count = new int[10];
		int box=0;
		int answer=0;


		for(int i=0;i<n*3;i++){
			int input = stdIn.nextInt();
			if(input==10) input =0;
			
			count[input] += 1;
			if(count[input]==2){
				count[input] -= 2;
				answer += 1;
			}

		}

		for(int  i=0;i<10;i++){
			box+=count[i];
		}

		answer += (int)(box/4);

		System.out.println(answer);
	}
}