(defun main (&rest argv)
  (declare (ignorable argv))
  (let* ((*read-default-float-format* 'double-float)
         (m (read)))
    (dotimes (_ m)
      (let* ((a (read))
             (b (read))
             (c (float (read) 0d0)))
        (format t "~14,12f~%" (cond ((zerop a) (exp (expt c (/ 1d0 b))))
                                    ((zerop b) (expt c (/ 1d0 a)))
                                    (t (let* ((logc (log c))
                                              (n 3)
                                              (logn (log n))
                                              (f (- (+ (* a logn) (* b (log logn))) logc)))
                                         (loop while (> (abs f) double-float-epsilon) do
                                                 (decf n (/ f (/ (+ a (/ b (log n))) n)))
                                                 (setf logn (log n)
                                                       f (- (+ (* a logn) (* b (log logn))) logc))
                                                 (loop while (<= n 1d0) do (incf n 0.2d0)))
                                         n))))))))

(main)