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.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ABC083D {
    class Program {
        static void Main(string[] args) {
            string S = Console.ReadLine();
            int len = S.Length;
            int half = (len + 1) / 2;
            int center = (len % 2 == 0) ? len / 2 - 1 : len / 2;
            string mark = S.Substring(center, 1);
            bool ok = true;
            int i = 0;
            while (ok && half + i < len) {
                string low = (len % 2 == 0) ? S.Substring(center - i, 1) : S.Substring(center - i - 1, 1);
                string high = S.Substring(center + i + 1, 1);
                if (low != mark || high != mark) {
                    ok = false;
                } else {
                    i++;
                }
            }
            Console.WriteLine(half + i);
        }
    }
}