C
      SUBROUTINE draw(x1,y1,x2,y2,n)
      IMPLICIT NONE
      REAL*8 dx, dy, x1n, x2n, xmid, y1n, y2n, ymid, x1, y1, x2, y2
      INTEGER IR_, n
      IF(n .GT. 0) THEN
         dx = (x2 - x1)/3
         dy = (y2 - y1)/3
         x1n = x1 + dx
         y1n = y1 + dy
         x2n = x1 + 2*dx
         y2n = y1 + 2*dy
*       
         xmid = 0.5D0*dx - 0.866D0*dy + x1n
         ymid = 0.5D0*dy + 0.866D0*dx + y1n
         CALL draw(x1,y1,x1n,y1n,n-1)
         CALL draw(x1n,y1n,xmid,ymid,n-1)
         CALL draw(xmid,ymid,x2n,y2n,n-1)
         CALL draw(x2n,y2n,x2,y2,n-1)
      ELSE
         CALL GWline(IR_, REAL(x1), REAL(y1), REAL(x2), REAL(y2))
      END IF
      END