//#include <bits/stdc++.h>
#include <stdio.h>
#include <algorithm>
#include <iostream>
#include <string>
#include <vector>
#include <functional>
#include <map>
#include <iomanip>
#include <math.h> 
#include <stack>
#include <queue>
#include <bitset>
#include <cstdlib>
#include <tuple>
#include <cctype>
#include <ctype.h>
#include <set>
#include <sstream>
using namespace std;
#define int long long
#define rep(i,s,n) for(int i = s;i<n;i++)
#define repe(i,s,n) for(int i = s;i<=n;i++)
#define rrep(i,s,n) for(int i = (n)-1;i>=(s);i--)
#define all(v) (v).begin(),(v).end()
#define pb push_back
#define fi first
#define se second
#define chmin(a,b) a=min((a),(b))
#define chmax(a,b) a=max((a),(b))
typedef long long ll;
typedef pair<int, int>pint;
typedef vector<int>vint;
typedef vector<pint>vpint;
typedef pair<pint, int> P1;
typedef pair<int, pint> P2;
typedef pair<pint, pint> PP;
static const ll maxLL = (ll)1 << 62;
const ll MOD = 1000000007;
const ll INF = 1e18;

int N, M;
vpint v[200020];

signed main() {
	string s;

	cin >> s;

	if (s.length() % 2 == 1) {
		cout << "NO" << endl;
	}
	else {
		string s1;
		rep(i, 0, s.length() / 2) {
			s1 += s[i];
		}

		int len = s.length();
		rep(i, 0, len / 2) {
			s.erase(s.begin());
		}

		if (s1 == s) {
			cout << "YES" << endl;
		}
		else {
			cout << "NO" << endl;
		}

	}














	getchar();
	getchar();
	return 0;
}