Why output of code 'cout<<a<<++a<<a;' in c++ is 666 where a=5

Question

according to me it should be 566 please explain it

Answer 1

It's not. The behavior of that code is undefined. See:

https://www.sololearn.com/Discuss/989706/?ref=app

https://www.sololearn.com/Discuss/957040/?ref=app

https://www.sololearn.com/Discuss/1036434/?ref=app

https://www.sololearn.com/Discuss/1073271/?ref=app

Answer 2

What is the value of a?

Answer 3

thanks for clearing my doubt guys