} else {
                      int ch = op.getData();
                      if (dx > 0) {
                          if (offset >= con.limit || ch !=  target .setIndex(  offset ) )
                              return -1;
                          offset ++;
                      } else {
                          int o1 = offset-1;
                          if (o1 >= con.limit || o1 < 0 || ch !=  target .setIndex(  o1 ) )
                              return -1;
                          offset = o1;
                      }
                  }