import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String n = sc.next();
        int first = 0, end = n.length() - 1;
        boolean isPalindrome = true;
        
        while (first < end) {
            if (n.charAt(first) == n.charAt(end)) {
                first++;
                end--;
            } else {
                isPalindrome = false;
                break;
            }
        }
        
        if (isPalindrome) {
            System.out.println("yes");
        } else {
            System.out.println("no");
        }
    }
}

双指针的算法思想，可以去了解了解，我这里是java写的