#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
   
using namespace std;
typedef long long int ll;
typedef pair<int, int> P;

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