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 Python (3.4.3) (judge verdict: Wrong Answer)

import sys
#import numpy as np

stdin = sys.stdin

ri = lambda: int(rs())
rl = lambda: list(map(int, stdin.readline().split()))  # applies to numbers only
rs = lambda: stdin.readline().rstrip()  # ignores trailing space

S = list(input())
N = len(S)
answer = (N+1)//2
streak = 1
cur = None
result = 0
for x in S:
    if cur == x:
        streak += 1
    else:
        cur = x
        streak = 1
    if streak > result:
        result = streak

if result > answer:
    print(result)
    exit()

while answer < N:
    S2 = S[-answer-1:answer+2]
    if len(set(S2)) == 1:
        answer += 1
        continue
    else:
        break

print(answer)