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

public class Main {
	public static void main(String[] args) {
		BufferedReader buff = new BufferedReader(new InputStreamReader(System.in));

		try {
			int N = Integer.parseInt(buff.readLine());
			int sum = N * 3;
			int[] num = new int[10];

			for (int i = 0; i < N; ++i) {
				String[] box = buff.readLine().split(" ");
				for (int j = 0; j < box.length; ++j) {
					num[Integer.parseInt(box[j]) - 1]++;
				}
			}

			int ans = 0;
			for (int i = 0; i < 10; ++i) {

				if (num[i] >= 2) {
					ans += num[i] / 2;
					sum -= num[i] - (num[i] % 2);
					num[i] %= 2;
				}
			}
			if (sum >= 4) {
				ans += sum / 4;
			}

			System.out.println(ans);
		} catch (NumberFormatException e) {

		} catch (IOException e) {

		}
	}
}