#include <iostream>
#include <cstring>
using namespace std;

int main() {
    char S[21];
    int length, i;
    cin >> S;
    length = strlen(S);
    if (length % 2) cout << "NO";
    else {
        for (i = 0; i < length / 2; ++i) {
            if (S[i] != S[length / 2 + i]) break;
        }
        if (i == length / 2) cout << "YES";
        else cout << "NO";
    }
}