import java.io.*;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.sql.Array;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class words {
    private static ArrayList<String> wordsIn = new ArrayList<>();
    private static ArrayList<String> wordsOut = new ArrayList<>();
    private static ArrayList<String> currentArray = new ArrayList<>();
    private static int currentCount;
    private static int countIn;
    public static void main(String[] args) throws IOException{
        fileRead("listOfWords");
        System.out.println(countIn);
        System.out.println(wordsIn);
        for (int i = 0; i < wordsIn.size(); i++){
            currentArray.add(wordsIn.get(0));
            backtrack(1);
        }
        fileWrite("outFile");
    }
    public static boolean existA(String a) throws IOException{
        for (String s : currentArray) {
            if (a.equals(s)) {
                return true;
            }
        }
        return false;
    }
    public static void backtrack(int k) throws IOException{
        for (int i = 0; i<wordsIn.size(); i++){
            String rightWord = wordsIn.get(i);
            String leftWord = currentArray.get(k-1);
            if ((rightWord.charAt(0)==leftWord.charAt(leftWord.length()-1))&&(existA(rightWord))){
                currentArray.add(rightWord);
                if(k>currentCount){
                    i = 0;
                    while (i<k+1){
                        wordsOut.add(currentArray.get(i));
                        System.out.println(wordsOut.get(i));
                        i++;
                    }
                    currentCount = k;
                }
                backtrack(k + 1);
                currentArray.clear();
            }
        }
    }
    public static void fileRead(String fileName) throws IOException{
        List<String> list = Files.readAllLines(Paths.get(fileName), StandardCharsets.UTF_8);
        countIn = Integer.parseInt(list.get(0));
        for (int i = 1; i < list.size(); i++) {
            wordsIn.add(list.get(i));
        }
    }
    public static void fileWrite(String fileName) throws IOException{
        FileWriter writer = new FileWriter(fileName, false);
            writer.write(wordsOut.size() + "\n");
        System.out.println("______________");
            for (String s: wordsOut){
                System.out.println(s);
                writer.write(s + "\n");
            }
        writer.close();
    }
}