O=C(c1ccccc1)c1ccc2[nH]c(-c3c(Cl)c(Cl)c(Cl)c(Cl)c3C(=O)N/N=C/c3ccc(Cl)cc3)nc2c1
Heavy atom refers to any atom that is not hydrogen. The heavy atoms in molecules are carbon, oxygen, nitrogen, and sulfur. How many heavy atoms are in the molecule?