(use gauche.array)
(use data.heap)

(define (read-number)
  (string->number (read-line)))

(define (read-numbers)
  (map string->number (string-split (read-line) #\space)))

(let* ((n (read-number))
       (c (read-number))
       (v (read-number))
       (s (read-numbers))
       (t (read-numbers))
       (y (read-numbers))
       (m (read-numbers)))

  (define graph (make-vector (+ n 1) '()))
  (define visited (make-vector (+ n 1) #f))
  (define times (make-array (shape 0 (+ n 1) 0 (+ c 1)) (ash 1 30)))
  (define heap (make-binary-heap :key cdr))

  (for-each
   (lambda (x y z w)
     (vector-set! graph x (cons (cons y (cons z w)) (vector-ref graph x  '()))))
   s t y m)

  (array-set! times 1 0 0)
  (binary-heap-push! heap (cons 1 0))

  (let loop ()
    (unless (binary-heap-empty? heap)
      (let* ((h (binary-heap-pop-min! heap))
	     (from (car h))
	     (weight (cdr h)))
	(vector-set! visited from #t)
	(let inner ((nodes (vector-ref graph from)))
	  (unless (null? nodes)
	    (let* ((node (car nodes))
		   (to (car node))
		   (cost (cadr node))
		   (time (cddr node)))
	      (for-each (lambda (i)
			  (if (>= (- i cost) 0)
			      (let1 t (+ time (array-ref times from (- i cost)))
				    (when (<= t (array-ref times to i))
				      (array-set! times to i t)))))
			(iota (+ c 1)))
	      (unless (vector-ref visited to)
		(binary-heap-push! heap (cons to (+ weight time)))))
	    (inner (cdr nodes)))))
      (loop)))

  (let1 val (apply min (map (lambda (i) (array-ref times n i)) (iota (+ c 1))))
	(print (if (= val (ash 1 30)) -1 val))))