#include <bits/stdc++.h>

#define int long long

using namespace std;
#define rep(i,s,n) for(int i = s;i<n;i++)
#define repe(i,s,n) for(int i = s;i<=n;i++)
#define rrep(i,s,n) for(int i = (n)-1;i>=(s);i--)
#define all(v) (v).begin(),(v).end()
#define pb push_back
#define fi first
#define se second
typedef long long ll;
typedef pair<int,int>pint;
typedef vector<int>vint;
typedef vector<pint>vpint;
typedef pair<pint,int> P1;
typedef pair<int,pint> P2;
static const ll maxLL = (ll)1 << 62;
const ll MOD=1000000007,INF=1e18;
int dy[]={-1,0,1,0};
int dx[]={0,1,0,-1};

string s;
 
signed main(){
	cin>>s;
	//cout<<s.size()%2<<endl;
	if(s.size()%2){
	    cout<<"NO"<<endl;
	    return 0;
	}
	bool can=true;
	rep(i,0,s.size()/2){
	    if(s[i]!=s[i+s.size()/2])can=false;
	}
	if(can)cout<<"YES"<<endl;
	else cout<<"NO"<<endl;
	
	
	
	return 0;
}