One mole of ideal gas with known constant volume specific heat is confined in the cylinder by the weightless frictionless piston. The rest of the cylinder is in vacuum. The spring exhorts the force on the piston, compressing the gas. In the absence of gas the spring is not deformed and the piston is in the leftmost position contacting the left side of the cylinder. The heat is transmitted to the gas through the left side of the cylinder. Find specific heat C exhibited by the gas in this process.