/*


Input: n
Output: n vertex coordinates for a comb polygon, in ccw order

Written by Joseph O'Rourke, with contributions by Min Xu.
Last modified: October 1998
Questions to orourke@cs.smith.edu.
--------------------------------------------------------------------
This code is Copyright 1997 by Joseph O'Rourke.  It may be freely
redistributed in its entirety provided that this copyright notice is
not removed.
--------------------------------------------------------------------
*/

# include <stdio.h>

# define DIM     2               /* Dimension of points */
typedef int     tPointi[DIM];   /* type integer point */
# define PMAX    10000           /* Max # of pts in polygon */
   
typedef tPointi tPolygoni[PMAX];/* type integer polygon */

/******************************************************************************/

int main ( void )

/******************************************************************************/
/*
  Discussion:

    This code is associated with "Computational Geometry in C" 
    (Second Edition), Chapter 1.  

    This code generates a comb polygon suitable for input to tri.c

  Modified:

    30 April 2007

  Author:

    Joseph O'Rourke, Min Xu
*/
{
# define X 0
# define Y 1

  int i;
  int j;
  int n;
  tPolygoni P;

  printf ( "n=" );
  scanf ( "%d", &n );

  for ( i = 0; i < n/2; i++ )
  {
    P[2*i][X] = n-2 - (2*i);
    P[2*i][Y] = 0;
    P[2*i+1][X] = n-2 - (2*i + 1);
    P[2*i+1][Y] = 10;
  }
  
  P[n-1][X] = ( n - 2 ) / 2;
  P[n-1][Y] = -2;

  printf ( "%d\n", n );
  for ( i = 0; i< n; i++)
  {
    printf ( "%d %d\n", P[i][X], P[i][Y] );
  }
  return 0;
# undef X
# undef Y
}