I dont understand , this is my output on my computer:

s1:c b a
s2:7 6 5 4 3 2 1

but tests show:

[Actual]
S1: [1234567]
S2: [abc]
[Expected]
S2: [cba]
S2: [7654321]
[Input]
S1: [1234567]
S2: [abc]

please explain what happens ?

check for non printable chars or extra line feeds

What?
expected:<u 3 ***[w 4 ****x 6 ******]z 6 ******>
but was: <u 3 ***[w 4 ****x 6 ******]z 6 ******>