I can't understand c language

Question

In the code above I got it from a challenge I didn't understand how can variable a change to 10

I wrote it and test it and I got 10 but when I print the addresses it is returned to 3 what did happen herr

https://code.sololearn.com/cM1JL668RCct/?ref=app

Answer 1

The above code is ambiguous, if you try it in different compilers , it will yield different outputs.

Answer 2

I accept you soo it musn't be in a challenge

Why do just c have this problem