import java.util.*;

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