A piston of mass M can move without friction inside a long vertical cylinder sealed from the bottom and opened from the top. The cylinder is filled with an ideal gas. At the equilibrium position, the piston is situated at the hight l0 from the bottom of the cylinder. The pressure outside of the cylinder is P0, the cross section of the cylinder and the piston is S. Find the period of small oscillations of the piston if it is displaced from the equilibrium position and then released. Assume that the process is adiabatic.