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.

Sample Input 1Copy

010

Sample Output 1Copy

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 2Copy

100000000

Sample Output 2Copy

8

Sample Input 3Copy

00001111

Sample Output 3Copy

4