import java.util.Arrays;
import java.util.Scanner;

public class Main {

    static final int N = 5010;
    static int[][] a = new int[N][2];
    static int[] f = new int[N];

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        int n = Integer.parseInt(sc.nextLine());

        for (int i = 1; i <= n; i++) {
            String[] s = sc.nextLine().split(" ");
            a[i] = new int[]{Integer.parseInt(s[0]), Integer.parseInt(s[1])};
        }

        Arrays.sort(a, 1, n + 1, (o1, o2) -> o1[1] - o2[1]);//随便按照一端排序另一端求上升子序列即可

        int res = 0;
        for (int i = 1; i <= n; i++) {
            f[i] = 1;
            for (int j = 1; j < i; j++) {
                if (a[i][0] > a[j][0]) f[i] = Math.max(f[i], f[j] + 1);
            }
            res = Math.max(res, f[i]);
        }

        System.out.println(res);
    }
}