import java.util.*;

class Main {
	static Scanner sc = new Scanner(System.in);
	public static void main(String[] args) {
		
		
		String s = sc.next();
		String ans = "YES";
		if (s.length()%2 != 0) ans = "NO";
		else {
			if (!s.substring(0,s.length()/2).equals(s.substring(s.length()/2,s.length()))) {
				ans = "NO";
			}
		}
		
		System.out.println(ans);
		
	}
}