/* ===============================================================

        This program process the file Origin.txt (Darwin's book).
	It converts all upper-case letters to lower-case, remove
	all non-alpha-numeric characters except for the comma (,)
	the period (.) the space ( ) and the carriage return ("\n").

        by Nam Phamdo           March 9, 2000.

==================================================================== */

#include <stdio.h>

main ()

{
        char    w;


	w=getchar();
        while(w!=EOF){
	  if(w>='a' && w<='z')
            putchar(w);
	  if(w>='0' && w<='9')
            putchar(w);
	  if(w==',' || w=='.' || w==' ' || w=='\n')
            putchar(w);
	  if(w>='A' && w<='Z'){
	    w=w+32;
            putchar(w);
	  }
	  w=getchar();
        }
}