ln --symbolic ../../bysemester/s12/ai.pdf  ../../byexam/ai/s12.pdf
  ln --symbolic ../../bysemester/s12/ca.pdf  ../../byexam/ca/s12.pdf
  ln --symbolic ../../bysemester/s12/db.pdf  ../../byexam/db/s12.pdf
  ln --symbolic ../../bysemester/s12/hci.pdf  ../../byexam/hci/s12.pdf
  ln --symbolic ../../bysemester/s12/os.pdf  ../../byexam/os/s12.pdf
  ln --symbolic ../../bysemester/s12/pl.pdf   ../../byexam/pl/s12.pdf
  ln --symbolic ../../bysemester/s12/net.pdf   ../../byexam/net/s12.pdf