Input: 1  Output:  Expected: Special judge: No expected output available.
what this means? how to fix it?
Your output is wrong because there is one course and your course schedule is empty (it must contain that one course).
I guess there is no expected output because in general there can be many valid outputs here, not just one, and apparently the system then doesn't pick one because that could be misleading (though I think sometimes in such cases it still does pick and show an expected output, I'm not sure when/why).
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