Can anyone tell me that why the answer is 98 ?

Question

I have read that unions can store only one variable at a time and forgets as soon as the other one is declared. Here in the code only variable first and third[0] are declared, but second is not declared. And on printing the value of second it gives the value 98. Why???
Please! Check out the code once.
https://code.sololearn.com/ckK6OfQzEwHX/?ref=app