import java.io.*;
import java.util.*;
import java.util.Map.*;


public class Main_yukicoder202_1 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Printer pr = new Printer(System.out);

        int n = sc.nextInt();

        SortedMap<Integer, SortedSet<Integer>> xy = new TreeMap<>();

        int ret = 0;
        out:
        for (int i = 0; i < n; i++) {
        	int x = sc.nextInt();
        	int y = sc.nextInt();

        	for (Entry<Integer, SortedSet<Integer>> e : xy.subMap(x - 20, x + 20).entrySet()) {
        		int xtmp = e.getKey();
        		for (int ytmp : e.getValue().subSet(y - 20, y + 20)) {
        			if ((x - xtmp) * (x - xtmp) + (y - ytmp) * (y - ytmp) < 400) {
        				continue out;
        			}
        		}
        	}

			if (xy.containsKey(x)) {
				xy.get(x).add(y);
			} else {
				TreeSet<Integer> tmp = new TreeSet<>();
				tmp.add(y);
				xy.put(x, tmp);
			}
			ret++;
        }

        pr.println(ret);

        pr.close();
        sc.close();
    }

	@SuppressWarnings("unused")
	private static class Scanner {
		BufferedReader br;
		Iterator<String> it;

		Scanner (InputStream in) {
			br = new BufferedReader(new InputStreamReader(in));
		}

		String next() throws RuntimeException  {
			try {
				if (it == null || !it.hasNext()) {
					it = Arrays.asList(br.readLine().split(" ")).iterator();
				}
				return it.next();
			} catch (IOException e) {
				throw new IllegalStateException();
			}
		}

		int nextInt() throws RuntimeException {
			return Integer.parseInt(next());
		}

		long nextLong() throws RuntimeException {
			return Long.parseLong(next());
		}

		float nextFloat() throws RuntimeException {
			return Float.parseFloat(next());
		}

		double nextDouble() throws RuntimeException {
			return Double.parseDouble(next());
		}

		void close() {
			try {
				br.close();
			} catch (IOException e) {
//				throw new IllegalStateException();
			}
		}
	}

	private static class Printer extends PrintWriter {
		Printer(PrintStream out) {
			super(out);
		}
	}
}