(ql:quickload '(fiveam uiop))

(defun distance-1 (a b)
  (apply #'+
         (mapcar (lambda (e1 e2)
                   (abs (- e1 e2))) a b)))

(defun surface (cubes)
  (loop for a in cubes
        sum (- 6 (loop for b in cubes
                       count (= 1 (distance-1 a b))))))

(defun parse-coords (filename)
  (mapcar (lambda (l)
            (mapcar #'parse-integer (uiop:split-string l :separator ",")))
          (uiop:read-file-lines filename)))

(fiveam:test solutions
  (fiveam:is (= 64 (surface (parse-coords "eg-in"))))
  (fiveam:is (= 4474 (surface (parse-coords "input")))))