c----------------------------------------------------------------------
c     Solves
c
c     u'' = -u 
c
c     y(1) := u
c     y(2) := u'
c
c     y(1)' :=  y(2)
c     y(2)' := -y(1)
c
c----------------------------------------------------------------------
c     neq = 2
c----------------------------------------------------------------------

c----------------------------------------------------------------------
c     Implements differential equations.
c     Called by ODEPACK routine LSODA.
c----------------------------------------------------------------------
      subroutine fcn(neq,t,y,yprime)
         implicit    none

         include    'fcn.inc'

         integer     neq
         real*8      t,     y(neq),    yprime(neq)

         yprime(1) =  y(2)
         yprime(2) = -y(1)

         return
      end 

c----------------------------------------------------------------------
c     Implements Jacobian  (optional) ...
c----------------------------------------------------------------------
      subroutine jac
         implicit    none

         include    'fcn.inc'

         return
      end
