(defun r (x y)
(sqrt (+ (expt x 2) (expt y 2))))
(defun f628 (n)
(print (elt (sort (loop for x from 1 to n
nconc (loop for y upto x collect (r x y)))
#'<)
(1- n))))
(f628 1)
(f628 2)
(f628 5)
(f628 9)
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