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 Rust (1.15.1) (judge verdict: Runtime Error)

use std::vec::Vec;
use std::cmp::*;
fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>().split_whitespace().map(|e| e.parse().ok().unwrap()).collect()
}

fn main() {
    let s: Vec<char> = read::<String>().chars().collect();
    let n = s.len();
    let mut left = Vec::new();
    let mut right = Vec::new();
    let mut mid = Vec::new();
    if n % 2 == 1 {
      mid.push(s[(n+1)/2]);
    }

    for i in 0..n/2 {
      left.push(s[i]);
    }

    for i in (n+1)/2..n {
      right.push(s[i]);
    }

    let mut ans = right.len();
    let mut c = '0';
    if n % 2 == 1 {
      c = mid[0];
      ans += 1;
    } else {
      c = right[0];
    }

    left.reverse();
    for i in 0..right.len() {
      if c == right[i] && c == left[i] {
        ans += 1;
      } else {
        break
      }
    }

    println!("{}", ans);
    //println!("{:?}", s);
    //println!("{:?} {:?} {:?}", left, mid, right);
}