void test( int arg ) { <- I can't stand code without space between parameter and brackets
  
  displayNumber( arg, 14, 23 );
  
  if( arg < 10 ) {
    arg = test( arg + 1 );
  }

  else if( arg == -1 ||
           arg == -3 ||
           arg == -5 ) {
    return -1;
  }

  else { return 0; }
}