I need to find whether this language is context-free or not:
{u#v | u,v belong to {a,b,c}* and u is a substring of v}, over alphabet {a,b,c,#}
I suspect that it's not, and am trying to approach it via Pumping Lemma, but then I noticed that: any examples like a^n#a^n will not work, cos we can always make vwx in the second a^n such that after pumping, u is still a substring of v; then I tried playing around with # like a#ab^(n-3), but get lost with the choice of v and x since it's possible for one of them to be empty string.
This is homework so just a hint will be okay for me.