import java.util.Arrays;
import java.util.Scanner;

public class yuki3 {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner sc = new Scanner(System.in);
		String A = sc.nextLine();
		
		
		if(A.length() % 2 == 0) {
			String[] Bc = A.split("");
			String[] Box1 = new String[A.length()/2];
			String[] Box2 = new String[A.length()/2];
			
			for(int i =0 ; i < A.length()/2;i++) {
				Box1[i]=Bc[i];
			}
			
			for(int i =0 ; i < Box1.length;i++) {
				System.out.println(Box1[i]);
			}
			
			
			for(int i = A.length()/2 ; i < A.length();i++) {
				Box2[i-A.length()/2]=Bc[i];
			}
			
			for(int i =0 ; i < Box2.length;i++) {
				System.out.println(Box2[i]);
			}
			
			if( Arrays.equals(Box1, Box2)) {
				System.out.println("YES");
			}else {
				System.out.println("NO");
			}
		
		}else {
			System.out.println("NO");
		}
	}
}