#include <bits/stdc++.h>
#define rep(i, a, n) for(int i = a; i < n; i++)
#define repr(i, a, b) for(int i = a; i >= b; i--)
#define int long long
#define all(a) a.begin(), a.end()
#define chmax(x, y) x = max(x, y)
#define chmin(x, y) x = min(x, y)
using namespace std;
typedef pair<int, int> P;
const int mod = 1000000007;
const int INF = 1e15;

signed main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    string s;
    cin >> s;
    string t = s.substr(0, s.size() / 2);
    t = t + t;
    if(t == s) cout << "YES" << endl;
    else cout << "NO" << endl;
}