The Heung Shing Olympiad in Informatics (HSOI) is coming!

There are $N$ participants, and every participant of the heat event is given an ID, formed by $K$ lowercase alphabets. For example, IDs with $K = 4$ can be good, absd, oier, sdff... The left most alphabet is counted as the $1$^$st$ digit, and the right most is counted as the $K$^$th$ digit.

Some hackers in Hackerland attempt to hack the system storing those ID. Although the hack was not so successful, data corruption occured on the ID numbers! The data corruption is strange, the $x$^$th$ digit is chosen, and every participants' ID's $x$^$th$ digit may change to another digit (maybe the same as original). Also, the order of the IDs are shuffled.

As the competition is coming very soon, Alice has to recover the ID's as soon as possible. She asks you to help her. Given the orginal $N$ IDs, and the corrupted IDs. You have to help Alice to find out all the possible $x$.

The first line contains two integers $N$ and $K$, the number of participants and the length of IDs respectively.
The second line contains $N$ IDs, the orignal IDs before data corruption.
The third line contains $N$ IDs, the corrupted IDs.

Output $c$, the number of possible $x$ in the first line. For the next $c$ lines, output all the possible $x$. It is guaranteed that there exsists at least one possible $x$.

For all test data,
$1 \le N \le 1000$
$1 \le K \le 20$