#include<iostream>
#include<cstdio>
#include<cstdlib>
using namespace std;
int n,m,ans[10000]={0},answer=0;
struct hehe 
{
	int length,time;
}q[5005];
int cmp( const void *a , const void *b ) 
{ 
	struct hehe *c = (hehe *)a; 
	struct hehe *d = (hehe *)b; 
	if(c->length != d->length) return c->length - d->length; 
	else return c->time - d->time; 
} 
int main()
{
	freopen ("wooden.in","r",stdin);
	freopen ("wooden.out","w",stdout);
	cin>>n;
	for (int i=0;i<n;i++)
	{
		cin>>q[i].length>>q[i].time;
		ans[i]=1;
	}
	qsort(q,n,sizeof(q[0]),cmp);
	for (int i=n-1;i>=0;i--)
	{
		for (int j=i;j<n;j++)
		{
			if (q[i].time>q[j].time&&ans[j]>ans[i])
			{
				ans[i]=ans[j]+1;
			}
		}
		if (ans[i]>answer)
			answer=ans[i];
	}
	cout<<answer;
	return 0;
}