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 C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Linq;
using System.Collections.Generic;
class P
{
    static void Main()
    {
        string input = Console.ReadLine();
        List<int> list = new List<int>();
        list.Add(1);
        char chainc = input[0];
        input = input.Substring(1);
        foreach (var c in input)
        {
            if (c == chainc)
            {
                list[list.Count - 1]++;
            }
            else
            {
                list.Add(1);
                chainc = c;
            }
        }
        int sum = 0;
        double border = (double)(input.Length + 1) / 2;
        foreach (var i in list)
        {
            if (sum <= border && sum + i >= border)
            {
                int result = Math.Min(input.Length + 1 - sum, sum + i);
                Console.WriteLine(result);
                break;
            }
            sum += i;
        }
    }
}