Task

Take a   Natural Number   in a given base and return the sum of its digits:

   110         sums to   1
   123410   sums to   10
   fe16       sums to   29
   f0e16     sums to   29


[ I ~ S! d 0!=S L! + ] sS
 
1 lS x p
1234 lS x p
16 i
FE lS x p
F0E lS x p