Is it uniquely decodable

Bob wanted to tell his son the password of his CodeChef account, but as there are many people present in the surroundings, Bob encodes the password. Bob’s original password consists of digits $1, 2,$ and $3$ only. To encode the password, Bob decided: - Instead of the digit $1$, he would say $\texttt{ab}$. - Instead of the digit $2$, he would say $\texttt{aba}$. - Instead of the digit $3$, he wou