#include <iostream>
#include <conio.h>
#include <fstream>
#include <list>

using namespace std;

bool is_letter(char ch)
{
    if ((ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z'))
        return true;
    return false;
}

int my_strlen(char* s)
{
    int tmp = 0;
    while (s[tmp])
        tmp++;
    return tmp;
}

void my_strcpy(char* s1, char* s2)
{
    for (int i = 0; i < my_strlen(s2) + 1; i++)
        s1[i] = s2[i];
}

class my_string {
public:
    my_string() { string = new char[256](); size = 0; }
    my_string(char* s) : my_string() { size = my_strlen(s); my_strcpy(string, s); }
    my_string(const my_string& rhs);
    ~my_string() { delete[] string; }
    int getSize() const { return size; }
    char* getString() const { return string; }
    bool operator==(const my_string& rhs);
    bool start_eq_end() { return (this->string[0] == this->string[this->size - 1]) ? true : false; }
    void push_back(char ch) { this->string[this->size] = ch; size++; };
    void clear() { delete[] string; string = new char[256](); size = 0; }
    friend ostream& operator<<( ostream& stream, const my_string& s);
private:
    char* string;
    int size;
};

my_string::my_string(const my_string& rhs)
{
    this->size = rhs.size;
    this->string = new char[256]();
    my_strcpy(this->string, rhs.string);
}

ostream& operator<<(ostream& stream, const my_string& s)
{
    stream << s.string;
    return stream;
}

bool my_string::operator==(const my_string& rhs)
{
    if (this->size != rhs.size)
        return false;
    for (int i = 0; i < this->size; i++)
        if (this->string[i] != rhs.string[i])
            return false;
    return true;
}

//comparing function object for list::sort()
bool compare(my_string& s1, my_string& s2)
{
    if (s1.getSize() < s2.getSize())
        return s1.getSize() < s2.getSize();
    if (s1.getSize() > s2.getSize())
        return false;
    if (s1.getSize() == s2.getSize())
        for (int i = 0; i < s1.getSize(); i++)
            if (s1.getString()[i] < s2.getString()[i])
                return s1.getString()[i] < s2.getString()[i];
            else if (s1.getString()[i] > s2.getString()[i])
                return false;
    return false;
}

int main()
{
    ifstream fi("input.txt");
    ofstream fo("output.txt");

    my_string word;
    char ch;
    list<my_string> words;
    fi.get(ch);


    while (fi.peek() != EOF)
    {
        if (is_letter(ch))
        {
            while (is_letter(ch) && fi.peek() != EOF)
            {
                word.push_back(ch);
                fi.get(ch);
            }
            if (is_letter(ch) && fi.peek() != EOF)
                word.push_back(ch);
            //now we have word
            if (word.start_eq_end())
                words.push_back(word);
        }
        else
            fi.get(ch);
        word.clear();
    }

    words.sort(compare);
    words.unique();
    for (list<my_string>::iterator it = words.begin(); it != words.end(); it++)
        fo << *it << ' ';

    fi.close();
    fo.close();
    return 0;
}