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)

s = input()

def func(k):
    cnt = 0
    buf = 0
    arr = [0 for _ in s]
    arr.append(0)
    for i in range(len(s)) :
        if arr[i] == 1 :
            cnt -= 1
            buf += 1
        val = (int(s[i]) + cnt + buf)%2
        if val == 0:
            if buf > 0 :
                buf -= 1
                continue
            if i+k > len(s) : return False
            cnt += 1
            arr[i+k] += 1
    return True

l, r = 1, len(s)+1
while r-l > 1:
    mid = (r+l)//2
    # print(mid, func(mid))
    if func(mid) : l = mid
    else : r = mid

print(l)