#include<iostream>
#include<cmath>
//#include<string>
#include<string.h>
#include<stdio.h>
#include<algorithm>
using namespace std;
struct shu{
	int x;
	int y;
};
int main(){
	int n,n1=0,flag=0;
	shu a[1001];
	shu b[1001];
	int s=0,d1,d2;
	scanf("%d",&n);
	getchar();
	scanf("%d %d",&a[0].x,&a[0].y);
	b[n1].x=a[0].x;
	b[n1].y=a[0].y;
	for(int i=1;i<n;++i){
		flag=0;
		scanf("%d %d",&a[i].x,&a[i].y);
		for(int j=0;j<=n1;++j){
			if((a[i].x<=b[j].x&&a[i].y<=b[j].y)||(a[i].y<=b[j].x&&a[i].x<=b[j].y)){
				flag=1;
				b[j].x=a[i].x;
				b[j].y=a[i].y;	
				break;
			}
		}
		if(flag==0){
			n1++;
			b[n1].x=a[i].x;
			b[n1].y=a[i].y;
		}
		
	}
	printf("%d",n1+1);
	return 0;
}