Find the maximum Overhang

no.
Ans is 3m

It is an interesting sum.This is what i think.

First consider a system of 2 blocks.Max overhang=L/2.
At is pt. we notice that even if we tilt the above block a bit,the system still remains in equilibrium.
At this moment the normal acts at the contact pt(i.e. the edge), and produces no torque.
The wt also acts through this very pt. and net torque=0.
Apply this concept to the 3 block system remembering that the reactional force(normal force by lower block on upper produces no torque on the above block)

In general for a system of n identical blocks max. overhang=L/2(1+1/2+1/3....1/n)

i understood what you meant, but didnt get how to apply this for 3 blocks.
plz elaborate with a proper diagram if possible.