How to deal with this rejection email from the journal Mathematics of Computation? I am an undergraduate student, and i had submitted a paper manuscript to Mathematics of Computation, I choose this journal because of my supervisor, who advised me to submit my paper to this journal, but 2 weaks after the submission I received the following email.

Dear Professor XXX,
This message concerns the manuscript
XXXX by XXX
submitted to Mathematics of Computation.
We regret that we cannot consider it, in part because at present we have a large backlog of excellent articles awaiting publication. We are thus forced to return articles that might otherwise be considered. Thank you for considering Mathematics of Computation.
Sincerely,
XXXX Managing Editor, Mathematics of Computation
--- Sent via EditFlow by XXXX mathcomp@math.lsu.edu }}

So, how to deal with this situation ?
Are there any positives/negatives that can be taken ?
Should I submit the paper to another journal?   Or just submit it to the same journal at a later time?
Note that I informed the editors and the referees that I am an undergraduate student.
It is just a nice way to say no. Submit elsewhere.
This is called a desk reject; you will find more in this question What does the typical workflow of a journal look like? .
Note that Math Comp is one of the top journals in its field, so unless the paper was extremely good this was the expected outcome.