Construct a String

Consider a string $s$. The following operation can be performed on it successively several (possibly zero) times. - Select any non empty suffix of $s$ and append it to $s$ For example, if $s = \text{abcd}$, then $s$ can become either $\text{abcdd}$, $\text{abcdcd}$, $\text{abcdbcd}$ or $\text{abcdabcd}$ after one operation. Successive operations are now performed on the new string. You are giv