CF1890B.Qingshan Loves Strings

Qingshan has a string $s$ , while Daniel has a string $t$ . Both strings only contain $\texttt{0}$ and $\texttt{1}$ .

A string $a$ of length $k$ is good if and only if

• $a_i \ne a_{i+1}$ for all $i=1,2,\ldots,k-1$ .

For example, $\texttt{1}$ , $\texttt{101}$ , $\texttt{0101}$ are good, while $\texttt{11}$ , $\texttt{1001}$ , $\texttt{001100}$ are not good.

Qingshan wants to make $s$ good. To do this, she can do the following operation any number of times (possibly, zero):

• insert $t$ to any position of $s$ (getting a new $s$ ).

Please tell Qingshan if it is possible to make $s$ good.

The input consists of multiple test cases. The first line contains a single integer $T$ ( $1\le T\le 2000$ ) — the number of test cases. The description of the test cases follows.

The first line of each test case contains two integers $n$ and $m$ ( $1 \le n,m \le 50$ ) — the length of the strings $s$ and $t$ , respectively.

The second line of each test case contains a string $s$ of length $n$ .

The third line of each test case contains a string $t$ of length $m$ .

It is guaranteed that $s$ and $t$ only contain $\texttt{0}$ and $\texttt{1}$ .

For each test case, print "YES" (without quotes), if it is possible to make $s$ good, and "NO" (without quotes) otherwise.

You can print letters in any case (upper or lower).

In the first test case, $s$ is good initially, so you can get a good $s$ by doing zero operations.

In the second test case, you can do the following two operations (the inserted string $t$ is underlined):

1. $\texttt{1}\underline{\texttt{010}}\texttt{11}$
2. $\texttt{10101}\underline{\texttt{010}}\texttt{1}$

and get $s = \texttt{101010101}$ , which is good.

In the third test case, there is no way to make $s$ good after any number of operations.