#include<iostream>
#include<string>
using namespace std;
#define int long long
#define rep(i,n) for(int i = 0; i < n; i++)
#define INF (long long)(1e18)
#define MOD (int)(1e9+7)
#define MAX_V

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