#include<iostream>
#include<algorithm>
using namespace std;
int n,f[5005];
pair<int,int>city[5005];
int main()
{
int i,ans=0,j;
scanf("%d",&n);
for(i=0;i<n;i++)scanf("%d%d",&city[i].first,&city[i].second);
sort(city,city+n);
for(i=0;i<n;i++){
f[i]=1;
for(j=0;j<i;j++)if(city[i].second>city[j].second)f[i]=max(f[i],f[j]+1);
ans=max(ans,f[i]);
}
printf("%d\n",ans);
return 0;
}