Problem on spring equilibrium and energy conservation.

Q) Two blocks A and B of mass m and 2m respectively are connected by ends of an ideal spring of spring constant k as shown if figure. Block A is pressed by a force F and when the system in equilibrium, the force f is removed suddenly, Find the minimum compression in the spring so that the block B jumps off the ground.
Problem from chapter Newtons laws of motion. This will be helpful to IIT-JEE aspirants and other competitive exams like KVPY and Olympiads.