2.5 g of protein containing only glycine $\left(\mathrm{C}_2 \mathrm{H}_5 \mathrm{NO}_2\right)$ s dissolved in water to make 500 mL of solution. The osmotic pressure of this solution at 300 K is found to be $5.03 \times 10^{-3}$ bar. The total number of glycine units present in the protein is ____ (Given : R = 0.083 L bar $\left.\mathrm{K}^{-1} \mathrm{~mol}^{-1}\right)$