How to count number of C-u prefixes?

[Jean Louis]

I would like this  function to give me number of  times I have pressed
C-u, and here is the attempt to solve it:

(defun how-many-times (&optional prefix query)
  (interactive "p")
  (let* ((times (if (> prefix 1) (1+ (/ (sqrt prefix) 4)) 1)))
    (message "Times %s" times)))

M-x how-many-times = 1

C-u M-x how-many-times = 1.5, but I would like 1 as answer.

C-u C-u M-x how-many-times = 2.0 which is what I expect
 
C-u C-u C-u M-x how-many-times = 3.0 which is what I expect

C-u C-u C-u C-u M-x how-many-times = 5.0 which I don't expect

I would like to simply count the number of pressed C-u prefixes.


Jean

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