Problem:
Score : 500 points

Problem Statement

You are given a string S consisting of 0 and 1.
Find the maximum integer K not greater than |S| such that we can turn all the characters of S into 0 by repeating the following operation some number of times.

Choose a contiguous segment [l,r] in S whose length is at least K (that is, r-l+1\geq K must be satisfied). For each integer i such that l\leq i\leq r, do the following: if S_i is 0, replace it with 1; if S_i is 1, replace it with 0.

Constraints

1\leq |S|\leq 10^5

S_i(1\leq i\leq N) is either 0 or 1.

Input

Input is given from Standard Input in the following format:

S

Output

Print the maximum integer K such that we can turn all the characters of S into 0 by repeating the operation some number of times.

Sample Input 1

010

Sample Output 1

2

We can turn all the characters of S into 0 by the following operations:

Perform the operation on the segment S[1,3] with length 3. S is now 101.

Perform the operation on the segment S[1,2] with length 2. S is now 011.

Perform the operation on the segment S[2,3] with length 2. S is now 000.

Sample Input 2

100000000

Sample Output 2

8

Sample Input 3

00001111

Sample Output 3

4

Solution in OCaml (4.02.3) (judge verdict: Wrong Answer)


open Scanf
open Printf

let id x = x

let rec for_iter a b f = if a >= b then [] else let x = f a in x :: for_iter (a+1) b f

let () =
  let s = scanf " %s" id in
  let s_len = String.length s in
  for_iter 0 s_len (fun i ->
    if s.[i] = '1' then max (min (i+1) (s_len-i)) (max i (s_len-1-i))
    else s_len)
  |> List.fold_left min s_len
  |> printf "%d\n"