/* -*- coding: utf-8 -*-
 *
 * 739.cc:  No.739 大事なことなので2度言います - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

/* typedef */

/* global variables */

/* subroutines */

/* main */

int main() {
  string s;
  cin >> s;

  int n = s.size();
  if (! (n & 1)) {
    int nh = n / 2;
    bool ok = true;
    for (int i = 0; ok && i < nh; i++)
      ok = (s[i] == s[nh + i]);

    if (ok) {
      puts("YES");
      return 0;
    }
  }

  puts("NO");
  return 0;
}