Swaps in a String

You are given a string $S$ that contains of the characters $A$, $B$ or $C$ only. In one operation, you can do either of the following: - Choose an occurrence of $\text{AB}$ in the string, convert it to $\text{BA}$. - Choose an occurrence of $\text{BC}$ in the string, convert it to $\text{CB}$. Note that you are only allowed to operate on adjacent elements. Find the maximum number of operations