#include <iostream>
#include <string>
int main() {
  using namespace std;
  string a, b;
  int x = 1;
  getline(cin, a);
  for (int i = 2; i <= a.size(); i++)
    for (int j = 0; j < a.size() - i + 1; j++, x = 1) {
      b = a.substr(j, i);
      for (int k = 0; k < i / 2; k++)
        if (b[k] != b[i - 1 - k]) x = 0;
      if (x == 1) cout << b << endl;
    }
}