I went through 5 rounds with Microsoft , in the 5th round after we had almost run out of time, interviewer asked a math question, this round in particular was a system design round, as I was exhausted and my brain was not able to switch to match context (with the given explaination I was not able to imagine the core of the problem to be simple math) I struggled and took more time did not come up with elegant solution but solved it, interviewer was clearly not impressed and called out why I took a complex route to solve it, for this primary reason is I was exhausted with all design thinking and talking, what started as great round ended cold.

Do I have a chance for a hire, even if feedback from this round (considering the fact that interviewer did mention that he was happy with the design before moving onto math problem at the nth minute, ah luck !!!!) is negative ?

Any one with similar experience ? what was the out come ?