#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <iomanip>
#include <stack>
#include <algorithm>
#include <string>
#include <map>
#include <iterator>
#include <set>
#include <queue>
#include <bitset>

using namespace std;


int main() {

    string S;
    cin >> S;
    int N = S.size();

    bool ok = true;
    for (int i = 0; i < N / 2; ++i) {
        if (S[i] != S[i + N/2]) {

            ok = false;
            break;
        }
    }

    cout << (ok ? "YES" : "NO") << endl;
    return 0;
}