I'm getting WA in test 1 and here's the judge respone :
The submission ID : 431231.
Test: #1, time: 30 ms., memory: 42328 KB, exit code: 0, checker exit code: 1, verdict: WRONG_ANSWER
Input
hhoowaaaareyyoouu
Output
wre
Answer
wre
Checker Log
wrong answer 1st words differ - expected: 'wre', found: 'wre'
I had the same problem. In output was unwriteable symbol.
UPD: As NULL characters are "invisible", you saw such strange log message from the judge protocol.
UPD2: Oh I am wrong to show the code for explanation. But you can view the output in some editors (e.g. vim) that there are extra characters.
shater