Another birthday present

i am having a doubt in a solution of this question
though the solution is correct but how anyone can think about that

link to the question is

link to the solution is

@sahil_bhutada @tmwilliamlin @akshitm16 help
@avinash_akhil @everule1 @cubefreak777 @s_h_shahin
plz help

Post link to the Q and your submission to get help from community!

And remove the unformatted code from your post.

The send link you provided is not your submission. It is someone’s else codechef account.

i have a doubt in his solution only