O=C(c1ccccc1)c1ccc2c(c1)N=C1CCCC(O)=C1C1c3ccccc3C(=O)N21
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?