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

char S[ 100 ];
char T[ 100 ];

int main()
{
int i;

	ios::sync_with_stdio( false );
	cin.tie( 0 );

	cin >> S;

	i = strlen( S );
	i /= 2;

	strncpy( T, S, i );


	if( strcmp( T, S + i ) == 0 )
		cout << "YES" << endl;
	else
		cout << "NO" << endl;

	return 0;
}