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 PyPy3 (2.4.0) (judge verdict: Accepted)

# -*- coding: utf-8 -*-
import sys
sys.setrecursionlimit(10**9)
INF=10**18
MOD=10**9+7
input=lambda: sys.stdin.readline().rstrip()
YesNo=lambda b: bool([print('Yes')] if b else print('No'))
YESNO=lambda b: bool([print('YES')] if b else print('NO'))
int1=lambda x:int(x)-1

def main():
    S=list(map(int,list(input())))
    N=len(S)
    if N%2==0:
        left=N//2-1
        right=N//2
        ans=N//2
        if S[left]==S[right]:
            x=S[left]
            while left-1>=0 and S[left-1]==x:
                left-=1
            while right+1<N and S[right+1]==x:
                right+=1
            ans+=min(N//2-left,right-N//2+1)
    else:
        left=N//2
        right=N//2
        x=S[N//2]
        ans=N//2+1
        if left-1>=0 and S[left-1]==x:
            while left-1>=0 and S[left-1]==x:
                left-=1
        if right+1<N and S[right+1]==x:
            while right+1<N and S[right+1]==x:
                right+=1
        ans+=min(N//2-left,right-N//2)
    print(ans)

if __name__ == '__main__':
    main()