fn main() {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    let s: &str = s.trim().split('\n').next().unwrap().trim();
    let n = s.len();
    println!("{}", if &s[0..n/2] == &s[n/2..n] {"YES"} else {"NO"}) 
}