Problem: three piece puzzle

Code: three+piece+puzzle/tails_1700550246

Nibbles version: 0.2 | 0.21 | 0.22 | 0.23 | 0.24 | 0.25 | 1.00

Format: Compact | Simple | +Type | Table | JSON | .nbl (DeBruijn) | .nbl (names)

+ (concat):[chr] 
    + (concat):[[chr]] 
        =~ (group by (also sorts)):[[[chr]]] 
            % (split (remove empties)):[[chr]] 
                @ (= fstLine):[chr] 
                ~ (auto = words):auto 
            / (foldr1):int <--arg( A:[chr] ) 
                . (map):[int] 
                    $ (= A):[chr] 
                    , (length):int <--arg( B:chr ) 
                        `% (split list (keep empties)):[[chr]] 
                            ;$ (= fstLine):[chr] 
                            $ (= B):chr 
                - (subtract):int <--arg( D:int C:int ) 
                    (implicit arg = D):int 
                    (implicit arg = C):int