I've been struggling hard to overcome WA4 and WA9...
In the problem statement, it says "Sentences in a message consist of words, spaces and punctuation marks".
Then I've made these test cases and got AC in one go... :)
Try these cases if u get WA...

Case 1:
WHO ARE UUUUUUUUUUUUUUUUUUU
UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU?
CANT U SEE IT ?
Ans:
Who are uuuuuuuuuuuuuuuuuuu
uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu?
Cant u see it ?

Case 2:
 WHO ARE UUUUUUUUUUUUUUUUUUU
UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU?
CANT U SEE IT ?
Ans:
 Who are uuuuuuuuuuuuuuuuuuu
uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu?
Cant u see it ?

(It looks same to case 1, but it has an initial space character in the first line and I think this was causing WA9 for me...)

Case 3:
AND BEING CARELESS, WE ARE DESTROYING THE EARTH.
?????
WHO ARE UUUUUUUUUUUUUUUUUUU
UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU?
CANT U SEE IT ?

WHY DID U DO THIS?
UUUUUUUU
UUUUUUUU IDIOT.
BYE.

Ans:
And being careless, we are destroying the earth.
?????
Who are uuuuuuuuuuuuuuuuuuu
uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu?
Cant u see it ?

why did u do this?
Uuuuuuuu
uuuuuuuu idiot.
Bye.

Case 4:
...ARE U THERE STILL?
PLEASE, ANSWER MEEEEEEEEE ,
ANSWER ME , ANSWER ME...
PLEASE
Ans:
...Are u there still?
Please, answer meeeeeeeee ,
answer me , answer me...
Please



Let me know if any1 finds any error...
Thanks.