C :

#include "stdio.h"
#include "stdlib.h"
int n,max;
int a[5000],b[5000],c[5000];
int main()
{
	int i,j,k;
	scanf("%d",&n);
	for(i=0;i<n;i++)
	{
		scanf("%d%d",&a[i],&b[i]);
		c[i]=1;
	}
	for(i=0;i<n;i++)
	{
		for(j=0;j<i;j++)
			if(a[i]<a[j])
			{
				k=a[i],a[i]=a[j],a[j]=k;
				k=b[i],b[i]=b[j],b[j]=k;
			}
			if(a[i]==a[j]&&b[i]<b[j])
			{
				k=a[i],a[i]=a[j],a[j]=k;
				k=b[i],b[i]=b[j],b[j]=k;
			}
	}
	for(i=1;i<n;i++)
	{
		for(j=0;j<i;j++)
		{
			if(b[i]>b[j]&&c[i]==c[j])
				c[i]++;
		}
	}
	max=0;
	for(i=0;i<n;i++)
	{
		if(max<c[i])
			max=c[i];
	}
	printf("%d\n",max);
	return 0;
}

C++ :

#include<cstdio>
#include<algorithm>
using namespace std;
struct p{int x;int y;};p a[5001];
int n,f[5001]={0},mmax=0;
int cmp(const p & a,const p & b)
{
    return a.y<b.y;
}
int main()
{
	scanf("%d",&n);
	for(int i=1;i<=n;i++) scanf("%d%d",&a[i].x,&a[i].y);
	sort(a+1,a+n+1,cmp);
	for(int i=1;i<=n;i++)
	   for(int j=1;j<=i;j++)
	   {
	   	  if(a[j].x<a[i].x&&f[j]>=f[i]) f[i]=f[j]+1;
	   	  if(mmax<f[i]) mmax=f[i];
	   }
	printf("%d",mmax+1);
}

Pascal :

type node=record
       father:longint;
       fm:longint;
       end;
type s=record
      x,y:longint;
      end;
var a:array[1..10050]of s;
    b:array[1..10050]of node;
    c:array[1..50000]of longint;
    i,j,k,n,max,t:longint;
begin
  readln(n);
  for i:=1 to n do
   begin
    read(a[i].x,a[i].y);
    b[i].fm:=1;
    b[i].father:=0;
   end;
    for i:=1 to n-1 do
    begin
      for j:=i+1 to n do
        if a[i].x>a[j].x then
          begin
            t:=a[i].x;
            a[i].x:=a[j].x;
            a[j].x:=t;
            t:=a[i].y;
            a[i].y:=a[j].y;
            a[j].y:=t;
          end;
    end;
  for i:=n-1 downto 1 do
    for j:=i+1 to n do
      begin
        if (a[i].y<a[j].y)and (b[i].fm<b[j].fm+1) then
         begin
           b[i].fm:=b[j].fm+1;
           b[i].father:=j;
           continue;
         end;
      end;
  max:=0;
  for i:=1 to n do
    if b[i].fm>max then
    begin
      max:=b[i].fm;
      k:=i;
    end;
  writeln(max);
  {repeat
    if b[k].father=0 then
      writeln(a[k].y)
      else
    write(a[k].y,' ');
    k:=b[k].father;
   until k=0;}
end.