import java.util.*;

public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(true){
            int a =sc.nextInt();
            if(a==0){
                break;
            }
            if(a==1){
                System.out.println(sc.next());
                continue;
            }


            String str[] = new String[a];
            for(int i = 0;i<a;i++){
                str[i]=sc.next();
                //System.out.println(str[i]);
            }



            int temp = 0;
            for(int j =1;j<str[0].length()+1;j++ ){
                String out = str[0].substring(str[0].length()-j);

                for(int i =1;i<a;i++){
                    if(str[i].length()<j){
                        //System.out.println("情况1");
                        out=str[i];
                        temp = 1;
                        break;
                    }

                    //System.out.println("out: "+out+" 比较" + str[i].substring(str[i].length()-j));


                    if(!out.equals(str[i].substring(str[i].length()-j))){
                        if(j==1){
                            //System.out.println("情况2");
                            out="";
                        }
                        else{
                            //System.out.println("情况3");
                            out=str[i].substring(str[i].length()-j+1);
                        }
                        temp = 1;
                        break;
                    }





                }
                if(temp==1){
                    System.out.println(out);
                    break;
                }
                if(temp==0 && j==str[0].length()){
                    System.out.println(str[0]);
                    break;
                }

            }



        }
    }
}