import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.Scanner;

public class Main {

    public static void sort( List<Obj> list ) {
        Collections.sort( list, new Comparator<Obj>() {

            public int compare( Obj o1, Obj o2 ) {
                    return o1.end - o2.end;
            }
        } );
    }

    public static void main( String[] args ) {
         List<Obj> list;
         Scanner sc = new Scanner(System.in);
         int n;
         while(sc.hasNext()){
             n = sc.nextInt();
             if(n==0) return;
            list = new ArrayList<Obj>();
             while(n>0){
                 int start = sc.nextInt();
                 int end = sc.nextInt();
                 Obj obj = new Obj( start, end, end-start );
                 list.add( obj );
                 n--;
                 sort(list);
             }
             System.out.println(solve(list));
         }
    }

    private static int solve( List<Obj> list ) {
        int max = 1;
        int end = list.get(0).end;
        for(int i=0;i<list.size();i++){
            if(list.get( i ).start >= end){
                end = list.get( i ).end;
                max++;
            }
        }
        return max;
    }

}

class Obj {

    public int start;

    public int end;

    public int dur;

    public Obj( int start, int end, int dur ) {
        this.start = start;
        this.end = end;
        this.dur = dur;
    }
}