#include <bits/stdc++.h>
#define INF 990000000
//22
using namespace std;

int main() {
string s;
cin>>s;
int fl=0;
for(int i=0;i<((int)s.size()+1)/2;i++){
if(s[i]!=s[i+((int)s.size()+1)/2])fl=1;
}
if(fl==0)
cout << "YES"<<endl;
else
cout << "NO"<<endl;





}