!----------------------------------------------------------------------------
!   compute bcain 
!   inputs:
!         2) position dlat,dlong,alt
!
!   outputs:
!         1) Bcain in MSO and IAU and it's magnitude
!         2) index indacting calculation is ok
!
!-----------------------------------------------------------------------------
      subroutine cain (dlat,dlong,alt,Btt,Bpp,Brr,Bx,By,Bz,B,ifail)
!-------------------------------------------------------------
!      DECLARATION 
!-------------------------------------------------------------
      implicit real (kind=8) (a-h,o-z)
      external cread, gfield
      character(2000) :: coeffs_cain_file ="@CAIN_COEF_DIR@/FSU_mars90"
      integer l
      common /trace/rm, maxln
     ! real dlat,dlong,alt,Btt,Bpp,Brr,Bx,By,Bz,B
      integer ifail
!------------------------------------------------------------
!     END OF DECLARATION 
!------------------------------------------------------------    
      rm = 3396.2
      l = 1
      ty = 1999.6493
      open (unit=12,file =trim(coeffs_cain_file))
      call cread (12,ty,l,maxln,a) 
      call gfield(dlat,dlong,alt,maxln,rm,Btt, Bpp, Brr, Bx,By,Bz,B)
      ifail = 1
      end