#include < iostream >
using   namespace  std;

struct  arr{
     int  x,y;
}a[ 1000 ];
int  n;
int  f[ 1000 ];
int  cmp( const   void *  no1, const   void *  no2){
    arr  * nox = (arr * )no1, * noy = (arr * )no2;
     if (nox -> x != noy -> x)  return  nox -> x - noy -> x;
     else   return  nox -> y - noy -> y;
}
int  main()
{
    freopen( " stick.in " , " r " ,stdin);
    freopen( " stick.out " , " w " ,stdout);
    scanf( " %d " , & n);
     for ( int  i = 0 ;i < n; ++ i) 
        scanf( " %d%d " , & a[i].x, & a[i].y);
    qsort(a,n, sizeof (arr),cmp);
     int  MAX = 0 ;
     for ( int  i = 0 ;i < n; ++ i){
        f[i] = 1 ;
         for ( int  j = i - 1 ;j >= 0 ; -- j)
             if (a[i].y < a[j].y && f[i] < f[j] + 1 )
                f[i] = f[j] + 1 ;
         if (f[i] > MAX) MAX = f[i];
    }
    printf( " %d\n " ,MAX);
     return   0 ;
}