//**********************
//*??????? **
//*?????? **
//*???1200012957 **
//*???2012-11-18 **
//***********************

int main ()
{
	char str[500];
	int i, j, k, len, m, n, count;
	cin.getline(str,500);
	len = strlen(str);
	// i + 1????????i???1??len - 1?
	for (i = 1; i < len; i++ )
	{
		// j??????????
		for (j = 0; j < len - i; j++ )
		{
			// ???i, j???????????????
			m = j;
			n = j + i;
			// ???????
			count = 0;
			// ?????????????????????
			while (str[m] == str[n] && m < n)
			{
				m++ ;
				n-- ;
				count++ ;
			}
			// ???????????????????count??[i / 2] + 1;
			if (count == i / 2 + 1)
			{
				// ?????????
				for (k = j; k <= j + i; k++ )
				{
					cout << str[k];
				}

				cout << endl;
			}
		}
	}

	return 0;
}
