(use scheme.vector)
(use gauche.collection)
(use util.combinations)

(let* ((n (read)))
  (define vec (vector-map char->integer (string->vector (number->string n))))
  (print (apply max
		#?=(let loop ((is (combinations (iota (vector-length vec)) 2)))
		     (cond ((null? is) '())
			   (else
			    (let ((vec-copied (vector-copy vec))
				  (pair (car is)))
			      (vector-swap! vec-copied (car pair) (cadr pair))
			      (cons (string->number (list->string (map integer->char vec-copied)))
				    (loop (cdr is))))))))))