Initially approved to treat psoriasis (a skin disorder) and rheumatoid arthritis, the drug tofacitinib has recently been found to also promote hair growth and restore hair loss (J. Invest. Dermatol. 2014, 134, 2988-2990). Identify the number of carbon atoms in tofacitinib, and the fill in all of the missing hydrogen atoms that are inferred by the drawing.