/*
 * huiwenzichuan.cpp
 *
 *  Created on: 2010-11-30
 *      Author:??
 *      ????????
 */
void find(char str[500])//????????????
{
   int i, j, k, t,length;
   length=strlen(str);//length???????
   for(i=2;i<=length;i=i+2)//????????????????????
   {
	   for(j=0;j<length-i+1;j++)//????????????
	   {
		  for(k=j;k<j+i/2;k++)
		  { if(str[k]!=str[2*j+i-1-k]) break;  }//??????????????????????
		  if(k==j+i/2)
		  {
			  for(t=j;t<j+i;t++)
			  {cout<<str[t];}
			  cout<<endl;
		  }//??????????????
	   }

   }
}
int main()
{
	char str[500];//??????
	cin >> str;
	find (str);//??????????
	return 0;
}