# code: http://golf.shinh.org/reveal.rb?Missing+Digit/tails_1644381918&nbb
# target Nibbles version: 0.23
# commenter version: 0.1.2.181

/ #(foldr):int 
    @ #(= fstLine):[chr] 
    477 #(integer):int <--arg( B:chr A:chr ) 
    - #(subtract):chr <--arg( D:chr C:int ) 
        @ #(= C):int 
        #(implicit arg = D):chr