public class main {
public static void main(String[] args) {
Scanner cin=new Scanner(System.in);
String input,str1,str2;
char char1[]=new char[500];
char char2[]=new char[500];
while(cin.hasNext()){
input=cin.nextLine();
for(int i=0;i<=input.length()/2-1;i++){
char1[i]=input.charAt(i);
}
int j=0;
if(input.length()%2==0){
for(int i=input.length()-1;i>=input.length()/2;i--){
char2[j]=input.charAt(i);
j++;
}
}
else{
for(int i=input.length()-1;i>input.length()/2;i--){
char2[j]=input.charAt(i);
j++;
}
}
str1=new String(char1);
str2=new String(char2);
if(str1.equals(str2)){
System.out.println("yes");
}
else{
System.out.println("no");
}
}

}