The molar specific heat of an ideal gas at constant pressure and constant volume is $\mathrm{C}_{\mathrm{p}} and \mathrm{C}_{\mathrm{v}} respectively. If \mathrm{R} is universal gas constant and \gamma=\frac{\mathrm{C}_{\mathrm{p}}}{\mathrm{C}_{\mathrm{v}}} then \mathrm{C}_{\mathrm{v}}=