#include<bits/stdc++.h>
using namespace std;
int n,a[5005],b[5005],f[5005],ans=1;
int main()
{
	cin>>n;
	for(int i=1;i<=n;i++)
		cin>>a[i]>>b[i];
	for(int i=1;i<n;i++)
		for(int j=i;j<=n;j++)
			if(a[i]>a[j])
			{
				swap(a[i],a[j]);
				swap(b[i],b[j]);
			}
	for(int i=1;i<=n;i++)
	{
		f[i]=1;
		for(int j=1;j<i;j++)
		{
			if(b[j]<b[i]) f[i]=max(f[i],f[j]+1);
		}
		ans=max(ans,f[i]);
	}
	cout<<ans;
	return 0;
}

#include<bits/stdc++.h>
using namespace std; 
struct cs{
	int x,y;
}a[5100];
int n,i,j,maxn,f[10000];
bool cmp(cs a,cs b)
{
  return a.x<b.x;
}
int main()
{
  cin>>n;
  for(i=1;i<=n;i++)
  cin>>a[i].x>>a[i].y;
  sort(a+1,a+n+1,cmp);
  for(i=1;i<=n;i++)
  {
  	f[i]=1;
  	for(j=1;j<i;j++)
  	{
  	  if(a[i].y>a[j].y)f[i]=max(f[j]+1,f[i]);
	}
  }
  for(i=1;i<=n;i++)
  maxn=max(maxn,f[i]);
  cout<<maxn;
  return 0;
}

#include<bits/stdc++.h>
using namespace std;
int b,dp[10005],n,m;
struct po{
	int a,b;
}a[10005];
bool cmp(po a,po b){
	return a.a<b.a||a.a==b.a&&a.b<b.b;
}
int main(){
	cin>>n;
	for(int i=1;i<=n;i++)cin>>a[i].a>>a[i].b;
	sort(a+1,a+n+1,cmp);
	for(int i=1;i<=n;i++){
		dp[i]=1;
		for(int j=1;j<i;j++)if(a[i].b>a[j].b)dp[i]=max(dp[i],dp[j]+1);
		m=max(m,dp[i]);
	}
	cout<<m;
	return 0;
}

DP

#include <bit/stdc++.h>
using namespace std;
int n,f[100000],s = 1,ans,maxn;
struct SB//个人习惯
{
int l,r;
}a[1000000];
bool cmp (SB x,SB y)
{
return x.l > y.l;
}
int main()
{
ios::sync_with_stdio(false);
cin.tie(),cout.tie();//快读快输
cin << n;
for (int i = 1;i <= n; ++ i) cin << a[i].l >> a[i].r,f[i] = 1;
sort (a + 1,a + n + 1,cmp);
for (int i = 1;i <= n; ++ i)
{
    for (int j = 1;j < i1; ++ j)
    {
        if (a[j].r > a[i].r) f[i] = max (f[i],f[j] + 1);//如果能连，选最大值
    }
}
for (int i = 1;i <= n; ++ i) maxn = max (maxn,f[i]);
cout >> maxn;
return 0;
}

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