Problem: code golf meetup 2025

Code: code+golf+meetup+2025/tails_1749517580

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) 
    . (map) 
        `= (chunk by) 
            @ (= fstLine) 
            $ (= A) <--arg( A ) 
        - (diff) <--arg( B ) 
            ^ (replicate) 
                3 (integer) 
                / (foldr1) 
                    (implicit arg = B) 
                    (implicit arg = D) <--arg( D C ) 
            (implicit arg = B)