#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <map>
#include <set>
#include <stdio.h>
#include <cstring>
#include <queue>
#include <stack>
#include <functional>
#include <random>
using namespace std;
#define Would
#define you


int main() {
	string h;
	cin >> h;
	if (h.length() % 2 == 0 && h.substr(0, h.length() / 2) == h.substr(h.length() / 2, h.length() / 2)) {
		cout << "YES" << endl;
		return 0;
	}
	cout << "NO" << endl;
}