Blocks on table!

Classical Mechanics Level 4

At a smooth horizontal table are two identical cubes of mass $m$ , connected by a spring of rigidity $k$ . The length of spring in the un-stretched state is $l_0$ . The right cube is linked to the load mass $m$ at the end. At some time the system is released and the system moves without initial velocity. Find the maximum distance (in cm) between blocks during the motion of the system.

[ $l_0 = 1 cm$ , $m = 3 kg$ , $k = 1000 N/m$ ]