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: Accepted)


#include <vector>
#include <iostream>
#include <algorithm>
#include <string>
#include <set>
using namespace std;

int main() {
	string str;
	cin >> str;
	//vector<int> s;
	vector<int> region;
	int n = str.length();
	int maxchain = 0;
	int last = -1;
	int chain = 0;
	int k = n;
	for (int i = 0; i < str.length(); ++i) {
		int val = 0;
		if (str[i] == '0') val = 0;
		else val = 1;

		if (last == -1) {
			last = val;
			chain = 1;
		}
		else if (last == val) {
		}
		else {
			region.push_back(chain);
			last = val;
			chain = 1;
			k = min(k, max(i, n - i));
		}
	}
	cout << k << endl;
}