#include<iostream>
#include<algorithm>
#include <vector>
#include<cmath>
using namespace std;
int main() {
	string S;
	cin >> S;
	if (S.size() % 2 != 0) {
		cout << "NO" << endl;
	}
	else {
		int cnt = 0;
		for (int ia = 0; ia < S.size() / 2; ia++) {
			if (S.at(ia) != S.at(ia + S.size() / 2)) {
				cnt++;
			}
		}
		if (cnt) {
			cout << "NO" << endl;
		}
		if (!cnt) {
			cout << "YES" << endl;
		}
	}
}