import java.util.Scanner;

class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        char S[] = new char[21];
        S = sc.next().toCharArray();
        sc.close();
        int length = S.length, i;
        if (length % 2 == 1) System.out.print("NO");
        else {
            for (i = 0; i < length / 2; ++i) {
                if (S[i] != S[length / 2 + i]) break;
            }
            if (i == length / 2) System.out.print("YES");
            else System.out.print("NO");
        }
    }
}