SUBROUTINE DROPIN(IQUAD,IX,IY)
      INCLUDE 'TREK.COM/-LI'
      INCLUDE 'TREK2.COM/-LI'
 10   CALL IRAN10(IX,IY)
      IF(QUAD(IX,IY) .NE. IHDOT) GO TO 10 
      QUAD(IX,IY)=IQUAD 
      RETURN      
      END