/*
 * huiwen string.cpp
 *??:???????????
 *  Created on: 2012-12-19
 *      Author: ???
 */



int main()
{
	char word[501];                //?????????
	cin.getline(word,sizeof(word));//?????
	int slen=strlen(word);         //???????
	int len=2,pos=0,num1,num2,i;   //??????,??????,??,????????????,
	char *p=NULL,*q=NULL;          //???????p,q
	for(len=2;len<=slen;len++)     //??????
	{
		if(num1==0&&num2==0)       //??????????(????)?????,????
			break;
		if(len%2==0)               //??????????
			num2=0;
		else                       //?????
			num1=0;
		for(pos=0;pos<=slen-len;pos++)//????
		{
			p=word+pos;
			q=word+pos+len-1;
			do
			{
				if(*q!=*p)            //?????
					break;
				else
				  {
					p++;
					q--;
				  }
			}while(q>p);
			if(q<=p)
			{
				for(i=0;i<len;i++)
				cout<<word[pos+i];   //?????
				cout<<endl;
				if(len%2==0)         //??
					num2++;
				else
					num1++;
			}
		}
	}
	return 0;
}