n := read ();

case 3 of
  a -> write (a)
| _ -> write (0)
esac;

case 3 of
  a -> write (a)
esac;

case 3 of
  a@_ -> write (a)
esac;

case `a (1, 2, 3) of
  `b             -> write (1)
| a@`a (_, _, _) -> case a of
                     `a (x, y, z) -> write (x); write (y); write (z)
		    esac
esac