R=RNSRD()
$(RATIONAL NUMBER SPECIAL READ.  THE RATIONAL NUMBER R IS READ FROM 
THE INPUT STREAM AND REDUCED TO LOWEST TERMS.  ANY PRECEDING BLANKS 
ARE SKIPPED.)
     SAFE C,R.
(1)  R1=IREAD().  C=CREADB().  IF C=$=/ THEN R2=IREAD() ELSE ( R2=1.
     BKSP ).  IF R1=0 THEN R=0 ELSE R=RNRED(R1,R2).  RETURN..