#include <stdio.h>
#include <stdlib.h>

#define MaxSize 200
#define ShowSort

typedef struct {
   int x, y;
} POINT;

POINT p[ MaxSize ];
int N;

void read_points( void );
int cmp_sort( const void *, const void * );
int cmp_graham( POINT, POINT, POINT );
void dump_points( int );
int graham_scan( void );
int cross( POINT, POINT, POINT );

main()
{
   int M;

   read_points();
   M = graham_scan();
   dump_points( M );
   return EXIT_SUCCESS;
}

void read_points( void )
{
   int xval, yval;

   N = 0;

   while ( scanf( "%d%d", &xval, &yval ) != EOF ) {
      N++;
      p[ N ].x = xval;
      p[ N ].y = yval;
   }
}

int cmp_sort( const void *ptr1, const void *ptr2 )
{
   int delta_x1, delta_x2, delta_y1, delta_y2, distsq1, distsq2, cr;
   POINT p0, p1, p2;

   p0 = p[ 1 ];
   p1 = *( ( POINT * ) ptr1 );
   p2 = *( ( POINT * ) ptr2 );

   if ( p1.x == p2.x && p1.y == p2.y )
      return 0;
      
   if ( ( cr = cross( p0, p1, p2 ) ) != 0 )
      return -cr;

   delta_x1 = p1.x - p0.x;
   delta_x2 = p2.x - p0.x;
   delta_y1 = p1.y - p0.y;
   delta_y2 = p2.y - p0.y;
   distsq1 = delta_x1 * delta_x1 + delta_y1 * delta_y1;
   distsq2 = delta_x2 * delta_x2 + delta_y2 * delta_y2;

   return distsq1 - distsq2;
}

void dump_points( int k )
{
   int i;

   printf( "\n\nDumping points\n" );

   for ( i = 1; i <= k; i++ )
      printf( "\tpoint %3d: %5d%5d\n", i, p[ i ].x, p[ i ].y );
}

int graham_scan( void )
{
   POINT temp;
   int min, i, M;
   
   min = 1;
   for ( i = 2; i <= N; i++ )
      if ( p[ i ].y < p[ min ].y )
         min = i;

   for ( i = 1; i <= N; i++ )
      if ( p[ i ].y == p[ min ].y && p[ i ].x < p[ min ].x )
         min = i;

   temp = p[ 1 ];
   p[ 1 ] = p[ min ];
   p[ min ] = temp;

   qsort( p + 2, N - 1, sizeof( p[ 0 ] ), cmp_sort );

#ifdef ShowSort
   printf( "After qsort\n" );
   dump_points( N );
   printf( "After dump_points\n\n" );
#endif
   
   p[ 0 ] = p[ N ];
   M = 2;

   for ( i = 3; i <= N; i++ ) {
      while ( cmp_graham( p[ M ], p[ M - 1 ], p[ i ] ) > 0 )
         M--;
      M++;
      temp = p[ M ];
      p[ M ] = p[ i ];
      p[ i ] = temp;
   }

   return M;
}

int cmp_graham( POINT p0, POINT p1, POINT p2 )
{
   int cr;

   if ( p1.x == p2.x && p1.y == p2.y )
      return 0;
      

   if ( ( cr = cross( p0, p1, p2 ) ) != 0 )
      return cr;

   return 1;
}

int cross( POINT p0, POINT p1, POINT p2 )
{
   int delta_x1, delta_x2, delta_y1, delta_y2;

   delta_x1 = p1.x - p0.x;
   delta_x2 = p2.x - p0.x;
   delta_y1 = p1.y - p0.y;
   delta_y2 = p2.y - p0.y;

   return delta_x1 * delta_y2 - delta_x2 * delta_y1;
}