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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<vector>
#include<string.h>
#include<string>
#include<set>
#include<limits.h>
#include<set>
#include<map>
#include<unordered_map>
#include<unordered_set>
#include<list>
#include<functional>
#include<stack>
#include<deque>
#include<queue>
using namespace std;

int ru[100001];
signed main() {
	string a; cin >> a;
	for (int i = 0; i < a.length(); i++) {
		ru[i + 1] = ru[i];
		if (a[i] == '1')ru[i + 1]++;
	}
	int l = 1, r = a.length() + 1;
	while (r - l > 1) {
		int t = (l + r) / 2;
		bool OK = false;
		for (int j = t; j <= a.length(); j++) {
			if (ru[j] - ru[j - t] == 0|| ru[j] - ru[j - t] == t) {
				OK = true;
			}
		}
		if (OK)l = t;
		else r = t;
	}
	cout << l << endl;
}