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: Wrong Answer)

use std::io;
use std::cmp;

fn read_line() -> String {
    let mut buf = String::new();
    io::stdin().read_line(&mut buf).ok();
    buf
}



fn main() {
    let str = read_line().chars().collect::<Vec<char>>();

    let mut v = Vec::new();

    let mut i = 0;
    while i < str.len()-1 {
        let c = str[i];
        let mut count = 1;
        i += 1;
        while i < str.len() && c==str[i] {
            i+= 1;
            count += 1;
        }
        v.push(count);
    }

    let mut l = 0;
    i = 0;
    while i < (v.len()+1)/2 {
        l += v[i];
        i += 1;
    }
    let mut r = 0;
    i = (v.len()+1)/2;
    while i < v.len() {
        r += v[i];
        i += 1;
    }
    println!("{}", cmp::max(l,r));
}