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: Accepted)

#include <stdio.h>
#include <string.h>
#define MIN(a, b) ((a) < (b) ? (a) : (b))

int main(void) {
  char s[100001], flag;
  int len, k, start, end, i;
  scanf("%s", s);
  len = strlen(s);
  k = (len+1) / 2;

  if (len % 2 == 0) {
    k = len / 2;
    if (s[k-1] == s[k]) {
      flag = s[k];
      for (start = k-1; flag == s[start-1]; start--);
      for (end = k; flag == s[end+1]; end++);
      k = MIN(len - start, end + 1);
    }
  } else {
    k = (len + 1) / 2;
    if (s[k-2] == s[k-1] && s[k-1] == s[k]) {
      flag = s[k];
      for (start = k-2; flag == s[start-1]; start--);
      for (end = k; flag == s[end+1]; end++);
      k = MIN(len - start, end + 1);
    }
  }
  printf("%d\n", k);

  return 0;
}