Siblings and Lego Blocks

Raisa and Muaz are little baby siblings. Their father brought a beautiful gift for them, a Lego blocks set which contains $n$ blocks. There is written a string $S_i$ in each i'th block of the Lego blocks$(1\leq i \leq n)$. All the strings are not distinct. Once while Muaz was sleeping, Raisa was playing alone with the blocks. Raisa was making a queue with the blocks. But instead of adding in the e