Two blocks $A$ and $B$ of equal mass $m=1 \mathrm{~kg}$ are lying on a smooth horizontal surface as shown in Fig. $4.27$. A spring of force constant $K=200 \mathrm{~N} / \mathrm{m}$ is fixed at one end of block $A$. Block $B$ collides with another end of the spring with velocity $v_{0}=2 \mathrm{~m} / \mathrm{s}$. What will be the maximum compression of the spring? [in decimeter $]$