#include<bits/stdc++.h>
using namespace std;
typedef pair<int,int> PII;
#define x first
#define y second
const int N=5010;
PII a[N];
int f[N];
int main()
{ 
	int n;
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		cin>>a[i].x>>a[i].y;	
	} 
	sort(a+1,a+n+1);
	int ans=0;
	for(int i=1;i<=n;i++)
	{
		f[i]=1;
		for(int j=1;j<i;j++)
		{
			if(a[i].y>a[j].y) f[i]=max(f[i],f[j]+1);
		}
		ans=max(ans,f[i]);
	}
	cout<<ans;
	return 0;
}