package test;

import java.util.Scanner;

public class test {
	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		String string = s.nextLine();
		
		char c[] = string.toCharArray();
		
		if (c.length % 2 == 0) {
			for (int i = 0; i < c.length / 2; i++) {		
				if (c[i] != c[i + c.length / 2]) {
					System.out.println("NO");
					break;
				}
				else if (i <= c.length / 2) {
					System.out.println("YES");
				}
			}
		}
		else {
			System.out.println("NO");
		}

		
		System.out.println();
		
		s.close();
		
	}
}