2.5 g of protein containing only glycine (C₂H₅NO₂) is 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 K^$-$1 mol^$-$1)