50分，求调

#include <bits/stdc++.h>
using namespace std;
int n,ans;
struct city{
	int a,b,h=1;
}c[10001];
bool cmp (city x,city y)
{
	return x.a>y.a;
}
int main()
{
	cin>>n;
	for (int i=1;i<=n;i++){
		cin>>c[i].a>>c[i].b;
	}
	sort (c+1,c+n+1,cmp);
	for (int i=1;i<=n;i++)
	{
		for (int j=1;j<=i;j++)
		{
			if (c[j].b>c[i].b&&c[j].h+1>c[i].h)
			{
				c[i].h=c[j].h+1;
			}
		}
	}
	for (int i=1;i<=n;i++){
		if (c[i].h>ans)
			ans=c[i].h;
	}
	cout<<ans;
	return 0;
}