case 1:

                     String user;
                     String pswd;
                     do{
                     System.out.print("AUTHENTICATION !");
                     System.out.print("Enter UserName\n");
                     user = input.next();
                     System.out.print("Enter Password:\n");
                     pswd = input.next();



                     index = users.search(user);
                     if (index<0){
                         System.out.println("step1\n\n");
                         index=teachers.search(user);
                         if (index<0)
                               try{
System.out.println("Step3\n\n");
                         if(teachers.getTeacher(index).Authenticate(user, pswd)){
                                System.out.println("Authentification Successful!\n\n");
                         }
                         else
                               throw new PassException();
                     }catch(PassException ex){
                       System.out.println(ex.getMessage());
                      }
                     // Authentification successful
                         if(index>0){
                           System.out.println("Teacher found");
                         }
                     }

                     else {
                             try{

                         if(users.getUser(index).Authenticate(user, pswd)){
                                System.out.println("Authentification Successful!\n\n");
                         }
                         else
                               throw new PassException();
                     }catch(PassException ex){
                       System.out.println(ex.getMessage());
                      }
                     // Authentification successful
                     }
                     }while( index == -1);