#include <bits/stdc++.h>  // g++ -std=c++14 -o a a.cpp

using namespace std;

typedef pair<int, int> P;
typedef long long ll;

#define rep(i, n) for(int i = 0; i < (n); i++)
#define repto(i, n) for(int i = 0; i <= (n); i++)
#define all(c) (c).begin(), (c).end()
#define uniq(c) c.erase(unique(all(c)), (c).end())
#define _1 first
#define _2 second
#define pb push_back
#define INF 1145141919
#define MOD 1000000007
#define DEBUG(x) cout << #x << ": " << x << endl;

__attribute__((constructor))
void initial() {
    cin.tie(0);
    ios::sync_with_stdio(false);
}

int main() {
    string s;
    cin >> s;
    int l = s.size();
    bool result = true;

    if (l % 2 != 0) {
        result = false;
    } else {
        int n = l / 2;
        
        rep(i, n) {
            if (s[i] != s[i + n]) result = false;
        }
    }
    if (result) {
        cout << "YES" << endl;
    } else {
        cout << "NO" << endl;
    }
}