int n = 7230702951; // invalid in java. The literal 7230702951 of type int is out of range

Did you figure this out? I'm struggling real hard for test case with 3263.

You are probably using up memory, and the test cases inputs a really large number.
As stated in the problem, you need to be able to handle this case:

int n = 7230702951;
Line.WhoIsNext(names, n) --> "Leonard"

If that case breaks, you'll need to refactor your solution until it doesn't break.

how do you actually use that code? I passed the run tests part but failed the submit tests. I was supposed to get -1 but i got 3263.10819218804. If i could see the test numbers maybe i can figure out what went wrong.

You can just System.out.println them