500        nstep     ! number of steps
0.1        dt        ! Delta t
100.0      am        ! mass of particles (MKS unit)
80.0d0     ak0       ! force constant (k) of spring
40d0       alength   ! length of spring
100d0      height    ! height of stage
00d0       gamma     ! friction of resistance
0          method    ! algorithm (method=0:velret,1:R-K(2th),2:R-K(4th))