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)

# -*- coding: utf-8 -*-

S = input()

l,r,r2 = 0,0,0
ans,prev = 0,0
while l < len(S):
    # prev,l,r,r2の4点で、3つの区間の情報を保持する
    if l == r == r2:
        while r < len(S) and S[l] == S[r]:
            r += 1
        r2 = r
    while r2 < len(S) and S[r] == S[r2]:
        r2 += 1
    # 今回区間
    sm = r - l
    # 前回区間
    prev_sm = l - prev
    # 次回区間
    nxt_sm = r2 - r
    # 両側に区間があれば追加
    sm += min(prev_sm, nxt_sm)
    ans = max(sm, ans)
    # 点を動かす
    prev = l
    l = r
    r = r2
print(ans)