#include <iostream>
#include <algorithm>
using namespace std;

const int N = 5010;
pair<int, int> a[N];
int n, f[N], res;

int main()
{
    cin >> n;
    for ( int i = 0; i < n; i ++ ) cin >> a[i].first >> a[i].second;
    sort(a, a + n);
    for ( int i = 0; i < n; i ++ )
    {
        f[i] = 1;
        for ( int j = 0; j < i; j ++ )
            if ( a[i].second > a[j].second ) 
                f[i] = max(f[i], f[j] + 1);
        res = max(res, f[i]);
    }
    cout << res;
    return 0;
}