#![allow(unused_imports)] use std::cmp::*; use std::collections::*; use std::io::Write; use std::ops::Bound::*; #[allow(unused_macros)] macro_rules! debug { ($($e:expr),*) => { #[cfg(debug_assertions)] $({ let (e, mut err) = (stringify!($e), std::io::stderr()); writeln!(err, "{} = {:?}", e, $e).unwrap() })* }; } fn main() { let s = read::<String>().chars().collect::<Vec<_>>(); if s.iter().all(|&x| x == s[0]) { if s.len() % 2 == 1 { println!("-1"); } else { println!("0"); } return; } if (0..=s.len() / 2).all(|i| s[i] == s[s.len() - 1 - i]) { // println!("{}", max(s.len() as i64 - 2, 0)); println!("0"); return; } println!("{}", s.len()); } 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() }