(define (read-list n)
  (cond [(zero? n) '()]
        [else (let1 x (read)
                    (cons x (read-list (- n 1))))]))

(define (read-list-list n)
  (cond [(zero? n) '()]
        [else (let1 m (read)
                    (cons (read-list m) (read-list-list (- n 1))))]))

(define (solve lx)
  (let loop ([lx lx])
    (let1 ly (filter (^x (not (null? x))) lx)
          (cond [(null? ly) '()]
                [else (append (map car ly) (loop (map cdr ly)))]))))

(define (main args)
  (let* ([n (read)]
         [ls (read-list-list n)])
    (print (string-join (map number->string (solve ls)) " ")))
  0)