#include <iostream>
#include <string>
#include <vector>
#include <set>
#include <cmath>
#include <stack>
#include <algorithm>
#include <iomanip>
#include <map>
#include <queue>
#include <functional>
#include <numeric>
using ll = long long;
using namespace std;

const ll MOD = 1e9 + 7;

int arr[32];
int main(void)
{
    string s;
    cin >> s;

    string t1 = s.substr(0, (s.size() + 1) / 2);
    string t2 = s.substr((s.size() + 1) / 2, s.size() / 2);

    //cout << t1 << " " << t2 << endl;
    if (t1 == t2)
        cout << "YES" << endl;
    else
        cout << "NO" << endl;
    return 0;
}