# print natural numbers as von Neumann ordinals
#```ci``s``s`ks``s`k`s`d`.{ck`k``s`kd`d`c.{.}
```c`.{.}``s``s`ks``s`k`s`d``r.{ck`k``s`kd``s`k.,`d`c.{`d``.{.}.}