#include <bits/stdc++.h>
using namespace std;

typedef unsigned long long ll;
typedef std::pair<int, int> P;

#define For(i, a, b) for(int i = (a); i < (b); i++)
#define Rep(i, n) For(i, 0, (n))
#define Rrep(i, n) for(int i = (n - 1); i >= 0; i--)
#define All(i, x) for(typeof(x.begin()) i = x.begin(); i != x.end(); i++)
#define ReAll(i, x) for(typeof(x.end()) i = x.end(); i != x.begin(); i--)
#define pb push_back

const int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
const int MAX = 100000;
const int INF = 1e9;
const int MOD = 1000000007;
const string END = "\n";

void solve(){
	string s; cin >> s;
	int l = s.size();
	bool flag = true;
	if(l % 2 != 0){
		flag = false;
	}else{
		Rep(i, l/2){
			if(s[i] != s[i + l/2]){
				flag = false;
			}
		}
	}
	if(flag) cout << "YES" << END;
	else cout << "NO" << END;
}

int main(){
	cin.tie(0);
   	ios::sync_with_stdio(false);
	solve();
	return 0;
}