Specific heats of an ideal gas at constant pressure and volume are denoted by $\mathrm{C}_{\mathrm{p}} and \mathrm{C}_{\mathrm{v}} respectively. If \gamma=\frac{\mathrm{C}_{\mathrm{p}}}{\mathrm{C}_{\mathrm{v}}} and \mathrm{R} it's the universal gas constant then \mathrm{C}_{\mathrm{v}}$ is equal to