#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <string>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <stdio.h>
using namespace std;
#define int long long
int MOD = 1000000007;
signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	string S;
	cin >> S;
	int N = S.size();
	if (N % 2 == 1) {
		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;
}