(defn has-n? [word n]
  (some #(= n %) (vals (frequencies word))))

(defn off-by-1? [[a b]]
  (->> (map vector a b)
       (filter (fn [[x y]] (not= x y)))
       ((fn [lst] (= 1 (count lst))))))

(defn part1 []
  (* (count (filter #(has-n? % 2) input))
     (count (filter #(has-n? % 3) input))))

(defn part2 []
  (->> (for [x input y input] (vector x y))
       (filter off-by-1?)
       (first)))