package net.ipipip0129.yukicoder.No739;

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        String scan_str = scan.nextLine();

        boolean ans = scan_str.length() % 2 == 0 &&
                scan_str.substring(0, scan_str.length() / 2)
                .equalsIgnoreCase(scan_str.substring(scan_str.length() / 2));
        System.out.println(ans? "YES" : "NO");
    }
}