(read-line)
(defparameter x (read-from-string (concatenate 'string "(" (read-line) ")" )))

(defparameter mae 0)
(defparameter ans 0)
(sort x #'<)

(if (= (length x) 1) (progn (format t "~d~%" ans) (quit)))
(setq mae (car x))
(setq x (cdr x))
(loop for i in x do
	;(format t "mae=~d ans=~d i=~d~%" mae ans i)

 	(setq ans (if (= (- i mae) 0) ans
			  (if (= ans 0) (- i mae ) (min ans (- i mae)))))
	(setq mae i)
)
(format t "~d~%" ans)