import java.util.Scanner;

public class Main {

	@SuppressWarnings("resource")
	public static void main(String args[]) {
		Scanner scanner = new Scanner(System.in);
		String s=scanner.next();
		
		for(int i=1;i<=s.length();i++) {
			String s1=s.substring(0,i);
			String s2=s.substring(i,s.length());
			if(s1.equals(s2)) {
				System.out.println("YES");
				return;
			}
		}
		System.out.println("NO");
	}
}