#include <iostream>

int main(void){
  std::string a;
  std::cin >> a;
  const char* ca = a.c_str();
  int count=0;
  
  if(a.length()%2!=0) std::cout << "NO" << std::endl;
  else{
    for(int i=0;i<a.length()/2;i++){
      if(ca[i]!=ca[i+a.length()/2]){
        std::cout <<"NO" << std::endl;
        break;
      }
      else count++;
    }
    if(count==a.length()/2) std::cout <<"YES" << std::endl;
  }
}