(define (find-cww s lim)
  (letrec*
    (
      (n (string-length s))
      (ans lim)
      (loop-i (lambda (i ans) (if (>= i (- n 2)) ans (loop-j i (+ i 1) ans))))
      (loop-j (lambda (i j ans) (if (>= j (- n 1)) (loop-i (+ i 1) ans) (loop-k i j (+ j 1) ans))))
      (loop-k (lambda (i j k ans) (if (>= k n) (loop-j i (+ j 1) ans) (let ((new-ans (if (and (char=? (string-ref s i) #\c) (char=? (string-ref s j) #\w) (char=? (string-ref s k) #\w)) (min ans (+ 1 (- k i))) ans))) (loop-k i j (+ k 1) new-ans)))))
    )
    (let
      (
        (result (loop-i 0 ans))
      )
      (if (= result lim)
        -1
        result
      )
    )
  )
)

(define yuki345
  (let
    (
      (s (read-line))
    )
    (display (find-cww s 101))
    (newline)
  )
)