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 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>
#include <string.h>

char S[114514];
int len;

int ziyuu[114514];

int cancelPoints[114514];

int main(void) {
	int onazi = 1;
	int i;
	int ok, ng;
	if (scanf("%114513s", S) != 1) return 1;
	len = (int)strlen(S);
	for (i = 1; i < len; i++) {
		if (S[i] != S[0]) {
			onazi = 0;
			break;
		}
	}
	if (onazi) {
		printf("%d\n", len);
		return 0;
	}
	ok = 1;
	ng = len;
	while (ok + 1 < ng) {
		int mid = ok + (ng - ok) / 2;
		int dekita = 0;
		int nyago;
		for (nyago = 0; nyago <= 1; nyago++) {
			int tunda = 0;
			int taseru = 0, tasu = 0, cancellable = 0, cancelled = 0;
			memset(ziyuu, 0, sizeof(*ziyuu) * len);
			if (nyago) {
				taseru++;
				tasu++;
				ziyuu[mid]++;
			}
			for (i = 0; i < len; i++) {
				tasu -= ziyuu[i];
				if ((S[i] - '0' + taseru) % 2 != 0) {
					if (taseru > tasu) {
						taseru--;
						if (i + mid <= len) cancelPoints[cancellable++] = i;
					} else if (i + mid <= len) {
						taseru++;
						tasu++;
						ziyuu[i + mid]++;
					} else if (cancelled < cancellable) {
						taseru++;
						if (i < cancelPoints[cancelled] + mid) {
							tasu++;
							ziyuu[cancelPoints[cancelled] + mid]++;
						}
						cancelled++;
					} else {
						tunda = 1;
						break;
					}
				}
			}
			if (!tunda) {
				dekita = 1;
				break;
			}
		}
		if (dekita) ok = mid; else ng = mid;
	}
	printf("%d\n", ok);
	return 0;
}

/*

1110

*/