import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Set;
import java.util.HashSet;

public class ProblemaC {

    private void createSuperString(Set<String> subStrings) {
        int totalStrings = subStrings.size();
        String[] match = new String[totalStrings];
        int i = 0;

        for(String superString : subStrings) {

            Set<String> temp = new HashSet<String>(subStrings);
            String maxSuperString = superString;
            while(temp.size() > 1) {

                String subString = "";
                String nextMaxSuperString = maxSuperString;

                for(String nextString : temp) {

                    if(!nextString.equals(nextMaxSuperString)) {

                        String superTemp = getSuperString(maxSuperString, nextString);
                        if (nextMaxSuperString.equals(maxSuperString) || nextMaxSuperString.length() > superTemp.length()) {
                            nextMaxSuperString = superTemp;
                            subString = nextString;
                        }
                    }
                }

                temp.remove(maxSuperString);
                temp.remove(subString);
                maxSuperString = nextMaxSuperString;
                temp.add(maxSuperString);
            }

            match[i] = maxSuperString;
            i++;
        }

        String bestAns = match[0];

        for(i = 1; i < match.length; i++) {
            if(bestAns.length() > match[i].length()) {
                bestAns = match[i];
            }
        }

        System.out.println("respuesta: "+bestAns);

    }

    private String getSuperString(String superString, String someString) {
        String result = superString;

        int endIndex = someString.length() - 1;

        while(endIndex > 0 && !superString.endsWith(someString.substring(0, endIndex)))  {
            endIndex--;
        }

        if(endIndex > 0) {
            result += someString.substring(endIndex);
        }
        else {
            result += someString;
        }

        return result;
    }

    public static void main(String arg[]) throws IOException {

    	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String lineain;
        String data[];
        Set<String> fragments;
        ProblemaC superStringCreator;

        int n;
        int k;


        while (true){
            fragments = new HashSet<String>();
            lineain = br.readLine();
            if (lineain.isEmpty()) return;
            data = lineain.split(" ");
            n = Integer.parseInt(data[0]);
            k = Integer.parseInt(data[1]);
            for (int i = 0; i != n; i++) {
                lineain = br.readLine();
                fragments.add(lineain);

            }
            superStringCreator = new ProblemaC();
            System.out.println("procesando: ");
            superStringCreator.createSuperString(fragments);

        }

    }
}