挺简单的，直接看代码

import java.util.*;
public class Main{
    static String f(String a){
        String b=a.substring(0,a.length()/2);
        String c=a.substring((a.length()+1)/2,a.length());
        if(b.equals(new StringBuilder(c).reverse().toString()))
            return "Yes!";
        else
            return "No!";
    }
    public static void main(String[] args) {
        Scanner scan=new Scanner(System.in);
        while(scan.hasNext())
            System.out.println(f(scan.next()));

    }
}