#include <iostream>
#include <algorithm>
#include <cstdio>
#include <string>

#define ll long long

using namespace std;

int main(){

   string s;
   cin>>s;
   if(s.length()%2){
       cout<<"NO"<<endl;
   }else{
       int flag=1;
       for(int i=0;i<s.length()/2;++i)
          if(s[i]!=s[i+s.length()/2]) flag=0;
        
        if(flag) cout<<"YES"<<endl;
        else cout<<"NO"<<endl;
   }
   
   return 0;
}