(define (same-character s l r)
  (let loop ([c 0]
             [i l]
             [j (- r 1)])
    (cond [(= i r) c]
          [(char=? (string-ref s i) (string-ref s j)) (loop (+ c 1) (+ i 1) (- j 1))]
          [else (loop c (+ i 1) (- j 1))])))

(define (main args)
  (let* ([s (read-line)]
         [sl (string-length s)])
    (print
     (let loop ([l 0]
                [r 1]
                [mx 0])
       (cond [(= l sl) mx]
             [(= r sl) (loop (+ l 1) r (max mx (same-character s l r)))]
             [else (loop l (+ r 1) (max mx (same-character s l r)))]))))
  0)