What is the maximum compression of the spring?

A mass m₁=[m] kg is at rest on a frictionless horizontal surface and connected to a wall by an ideal spring with a spring constant k = [k] N/m as shown in the figure. 

 A second mass m₂ =[mm] kg is moving to the left at speed v₀=[v] m/s. 

The two masses then collide elastically. 

 What is the maximum compression of the spring? 

Give your answer in m using 3 significant figures.