+--------------------+
                     |       Start        |
                     +--------------------+
                       |
                       |
                       v
    Until not done   +--------------------+   Until not done
  +----------------- |                    | -----------------+
  |                  |        Main        |                  |
  +----------------> |                    | <----------------+
                     +--------------------+
                       ^ Until not done |
                       +----------------+