```
0 0 0 x 0 0 | 2009355 2009356 2009357 2009358
      1          x               x            | unconfirmed
      2                          x       x
      3          x       x
      4                  x       x                    | after 2009356: 2 4 →  17 20
      5          x                       x
      6                  x               x
```