Bessie has a computer with a keyboard that only has two letters, M and O.
Bessie wants to type her favorite moo consisting of letters, each of which is either an M or an O. However, her computer has been hit with a virus. Every time she tries to type the letter O, every letter that she has typed so far flips, either from M to O or from O to M, before the O appears.
Is it possible for Bessie to type out her favorite moo?
Additionally, Bessie is given a parameter which is either or .
If , then Bessie only needs to determine whether it is possible to type out her favorite moo.
If , then Bessie also needs to give an example of a sequence of keystrokes to type so she can type out her favorite moo.
输入格式
The first line contains , the number of independent test cases () and ().
The first line of each test case has ().
The second line of each test case has . It is guaranteed that no characters will appear in besides and .
The sum of across all test cases will not exceed .
输出格式
For each test case, output either one or two lines using the following procedure.
If it is impossible for Bessie to type out , print on a single line.
Otherwise, on the first line print . Furthermore, if , on the second line, print a string of length , the characters in order that Bessie needs to type in order to type out her favorite moo. If there are multiple such strings, any will be accepted.
样例
样例输入 1
2 0
3
MOO
5
OOMOO
样例输出 1
YES
YES
样例输入 2
2 1
3
MOO
5
OOMOO
样例输出 2
YES
OMO
YES
MOOMO
数据范围与提示
As Bessie types out , this is how the letters change:
Before typing the first , Bessie has an empty string. Afterwards, she has the string .
After typing the first , the flips to , and then the is appended to form .
After typing the second , the flips to , and then the is appended to form .
After typing the second , Bessie has the string .
After typing the last , the string flips to , and then the is appended to form , as desired.
