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 Scala (2.13.1) (judge verdict: Accepted)

object Main extends App {
  val sc = new java.util.Scanner(System.in)
  val s = sc.next()
  val n = s.length
  val s1 = s.take(n/2).reverse
  val s2 = s.takeRight(n/2)
  if (n % 2 == 0) {
    if (s1.head == s2.head) {
      val idx1 = s1.indexWhere(_ != s1.head)
      val t1 = if (idx1 == -1) n/2 else idx1
      val idx2 = s2.indexWhere(_ != s2.head)
      val t2 = if (idx2 == -1) n/2 else idx2
      println(n/2 + t1.min(t2))
    } else {
      println(n/2)
    }
  } else {
    val t = s(n/2)
    val idx1 = s1.indexWhere(_ != t)
    val t1 = if (idx1 == -1) n/2 else idx1
    val idx2 = s2.indexWhere(_ != t)
    val t2 = if (idx2 == -1) n/2 else idx2
    println(n/2 + 1 + t1.min(t2))
  }
}