#include<cstdio>
#include<iostream>
#include<cstring>
#include<cmath>
#include<iomanip>
#include<queue>
#include<algorithm>
#include<vector>
#include<stack>
#include<set>
#include<map>
using namespace std;
#define LL long long
const int N=1e4+10;
const int INF=0x3f3f3f3f;
int n; 
struct node
{
	int n,s;
}a[N];
bool cmp(node a1,node a2)
{
	return a1.n<a2.n;
}
int dp[N];
int len;
int main()
{
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		cin>>a[i].n>>a[i].s;
	}
	sort(a+1,a+n+1,cmp);
	dp[++len]=a[1].s;
	for(int i=2;i<=n;i++)
	{
		if(dp[len]<a[i].s)
			dp[++len]=a[i].s;
		else
		{
			int pos=lower_bound(dp+1,dp+len+1,a[i].s)-dp;
			dp[pos]=a[i].s;
		}
	}
	cout<< len;
	
	return 0;
}