anchor.diff:  end do
   
   !!!!!!!!!!!!!!!!!  Integration of motion   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
  -do k =1, nstep
  +do k =1, 10000
       t = t0 + dt * k
       call integrate(f, eu, ek, part, vel, npart, a, r_cut2, e_cut, dt, e_tot, temp_k)
       part = part - l * nint(part/l)
  
positive.code: integer, parameter              :: npart=256
  real(pr)                        :: l, ln, t, a, r_cut2
  real(pr), parameter             :: temp=1.1_pr
  real(pr), parameter             :: dt=0.005, tf=5., t0 = 0.
  real(pr)                        :: eu, ek, temp_k, e_tot, e_cut
  !real(pr), dimension(1:3*npart)  :: f_old, x_new, v_new
  real(pr), dimension(1:3*npart)  :: part, f, vel
  
negative.code:     write(11, 36) t, ek, eu, e_tot, temp_k
  
  end do
  close(11)
  close(12)
  
  
  
  end program
  