subroutine SprObj( mode, n, x, f, g, nState,
     $                   cu, lencu, iu, leniu, ru, lenru )

      implicit           double precision (a-h,o-z)

      double precision   x(n), g(n)

      character*8        cu(lencu)
      integer            iu(leniu)
      double precision   ru(lenru)  

*     ------------------------------------------------------------------
*     This is funobj for problem Spring  (an optimal control problem).
*     ------------------------------------------------------------------
      integer            T
      parameter        ( zero = 0.0d+0 )

      T      = (n - 2)/2
      f      = zero
      jy     = 0
      jx     = T + 1

      do 50, k = 0, T
         jy    = jy + 1
         jx    = jx + 1
         u     = x(jx)
         f     = f  +  u**2
         g(jy) = zero
         g(jx) = u
   50 continue

      f = f / 2.0d+0

*     end of objective for Spring
      end