#include <cstdio>
#include <string>
#include <set>

using namespace std;

int equals[1024][1024];
int table[1025][1025];

int input(char s[1025])
{
  int c, len = 0;
  while (1) {
    c = getchar();
    if (feof(stdin)) { return len; }

    if ('a' <= c && c <= 'z') { s[len] = c - 0x20; len++; }
    else if ('A' <= c && c <= 'Z') { s[len] = c; len++; }
    else if (c == '\n') { s[len] = '\0'; break; }
  }
  return len;
}

void make_equals(char s[1025], int len)
{
  int i, j;
  for (i = 0; i < len; i++) {
    for (j = 0; j < len; j++) {
      if (s[i] == s[j]) { equals[i][j] = 1; }
      else { equals[i][j] = 0; }
    }
  }
}

/*
  Dynamic Programming

  table[leftmost][width]
    = table[leftmost+1][width-2] && equals[leftmost][leftmost+width-1]
*/

void make_table(char s[1025], int len)
{
  int leftmost, width;
  for (width = 1; width <= len; width++) {
    for (leftmost = 0; leftmost < (len - width + 1); leftmost++) {
      if (width == 1) { table[leftmost][width] = 1; }
      else if (width == 2) {
        if (s[leftmost] == s[leftmost+1]) { table[leftmost][width] = 1; }
        else { table[leftmost][width] = 0; }
      }
      else {
        table[leftmost][width]
          = table[leftmost+1][width-2] && equals[leftmost][leftmost+width-1];
      }
    }
  }
}

void println_sets(set<string> longests[1025])
{
  bool first = true;
  set<string> all;

  for (int i = 0; i < 1025; i++) {
    for (set<string>::iterator p = longests[i].begin();
         p != longests[i].end();
         p++) {
      all.insert(*p);
    }
  }

  for (set<string>::iterator p = all.begin();
       p != all.end();
       p++) {
    if (first) { first = false; }
    else { printf(" "); }
    printf("%s", p->c_str());
  }
  printf("\n");
}

void uniq_print(string &str, int len)
{
  int leftmost, width;
  set<string> centors[1025], longests[1025];

  for (width = 3; width <= len; width++) {
    for (leftmost = 0; leftmost < (len - width + 1); leftmost++) {
      if (table[leftmost][width]) {
        string substr = str.substr(leftmost, width);

        /* Clearly, "substr" is the same as the centor of the other string */
        if (leftmost > 0 && leftmost+width < len &&
            table[leftmost-1][width+2]) {
          centors[width].insert(substr);
          longests[width].erase(substr);
        }

        else {
          if (centors[width].find(substr) == centors[width].end()) {
            longests[width].insert(substr);
          }
        }
      }
    }
  }
  println_sets(longests);
}

int main()
{
  char s[1025]; int len;
  while (1) {
    len = input(s); if (feof(stdin)) { break; }

    make_equals(s, len);
    make_table(s, len);

    string str = string(s);
    uniq_print(str, len);
  }
  return 0;
}