import java.util.Scanner;

public class palindrome {

    static int palin(String s, int length) {

        int zt = 0;

        if (length == 1 || length == 0)

            return 1;

        if (s.substring(0, 1) .equals( s.substring(s.length() - 1, s.length()))){

            zt = 1;

            palin(s.substring(1, s.length() - 1), length-2);

        } else

            zt = 0;

        return zt;

    }

    public static void main(String[] args) {

        Scanner in = new Scanner(System.in);

        String s = in.next();

        int length = s.length();

        if (palin(s, length) == 1) {

            System.out.println("yes!");

        } else

            System.out.println("no!");

    }

}