PUPPYGM : Same solution getting AC and WA in different session ?

How same solution of same question can get WA in lunchtime and AC in practice session.
In lunch time:- https://www.codechef.com/viewsolution/7556418
In practice session :-https://www.codechef.com/viewsolution/7561655
In status it is showing “??”. What does it mean.

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