I think the test cases for problem D are wrong.I think that
there is a test case that includes more than n vertices or
more than 50 friends, because I got access violation.Then I
upped the array bounds and got Accepted, I may be wrong but
please check it out.

I first used di-graph, but can't get accepted, then I
turned to undirected-graph, but unexpectedly, got crush,
access violation