(print sum of 123 and 45)

  o
  > 123   B
 vo      A-+
  > 45    B|
  o      --+
  >      *  B
         o
   (check if 0)
         1
v  < B=- 0
 v   o * D- (div/10)
v       B *  <

v> * 1    o  ^
 F -R0  * 4 B
*| # <  -A8 v
 |      # <
#|
 -|            v   <
  |         *-|
  F           +B * ^
 #<         \F----
(ascii digit s)
(printed in)*-|
(reverse)    P-
            B