Here is the problem: 762C - Две строки.

When $$$a=\texttt{abcdcba}$$$ and $$$b=\texttt{abdcdba}$$$, the answer may be $$$\texttt{abcdba}$$$ or $$$\texttt{abdcba}$$$.

Why doesn't the problem have "if there are multiple solutions, print any"?

I also wonder whether the data contains this kind of input.