/******************************************/
/* hexbin.c 1.00                          */
/* by Adam M. Costello                    */
/* <amc@cs.wustl.edu>                     */
/*                                        */
/*  Translates a text file to a binary    */
/*  file according to the rules:          */
/*                                        */
/*  Define a hex character as any one of: */
/*    the digits 0 through 9              */
/*    the letters A through F             */
/*    the letters a through f             */
/*    a space                             */
/*    a tab                               */
/*                                        **************************/
/* On each line, characters are ignored until a colon is reached.  */
/* The colon is ignored, but subsequent characters are considered  */
/* until a non-hex character is reached.  This non-hex character   */
/* is ignored, as are all remaining characters.  Of the considered */
/* characters, all spaces and tabs are thrown out.  If the number  */
/* of remaining characters is odd, the last one is thrown out.     */
/* The remaining characters are taken in pairs to represent bytes. */
/*******************************************************************/

/* This is ANSI C code. */


#include <stdio.h>


#define hexval(c) ((c) >= '0' && (c) <= '9' ?  \
                     (c) - '0' :               \
                   (c) >= 'A' && (c) <= 'F' ?  \
                     (c) - 'A' + 10 :          \
                   (c) >= 'a' && (c) <= 'f' ?  \
                     (c) - 'a' + 10 :          \
                     -1                      )

                           
int main(int argc, char **argv)
{
  int c, ph, v[2];

  for (;;) {

    do if ((c = getchar()) == EOF) return 0;
    while (c != ':');

    ph = 0;

    for (;;) {
      do c = getchar();
      while (c == ' ' || c == '\t');
      if ((v[ph] = hexval(c)) < 0) break;
      if (ph) putchar(16 * v[0] + v[1]);
      ph = !ph;
    }

    while (c != '\n') {
      if (c == EOF) return 0;
      c = getchar();
    }

  }

}