package com.javarush.task.task22.task2207;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;
/*
Обращенные слова
*/
public class Solution {
public static List<Pair> result = new LinkedList<>();
public static void main(String[] args) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
String fileName = reader.readLine();
reader.close();
FileReader fr = new FileReader(fileName);
BufferedReader br = new BufferedReader(fr);
StringBuilder s = new StringBuilder();
while(br.ready()){
s.append(br.readLine());
s.append(" ");
}
String []mas = s.toString().split(" ");
br.close();
Pair pair = null;
for (int i = 0; i < mas.length-1; i++) {
for (int j =i+ 1; j < mas.length ; j++) {
String st = new StringBuilder(mas[j]).reverse().toString();
if(st.equals(mas[i])) pair = new Pair(mas[i],mas[j]);
if(!result.contains(pair)){result.add(pair);}
}
}
for(Pair p:result){System.out.println(p.toString());}
}
public static class Pair {
String first;
String second;
public Pair() {
}
public Pair(String string, String second) {
this.first = string;
this.second = second;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Pair pair = (Pair) o;
if (first != null ? !first.equals(pair.first) : pair.first != null) return false;
return second != null ? second.equals(pair.second) : pair.second == null;
}
@Override
public int hashCode() {
int result = first != null ? first.hashCode() : 0;
result = 31 * result + (second != null ? second.hashCode() : 0);
return result;
}
@Override
public String toString() {
return first == null && second == null ? "" :
first == null ? second :
second == null ? first :
first.compareTo(second) < 0 ? first + " " + second : second + " " + first;
}
}
}