O=S(=O)([O-])c1cc(/N=N/c2c(O)ccc3ccccc23)c2c(S(=O)(=O)O)cccc2c1.[Na+]
A rotatable bond is defined as any single non-ring bond, attached to a non-terminal, non-hydrogen atom. Amide C-N bonds are not counted because of their high barrier to rotation.  How many rotatable bonds does the molecule have?