diff --git a/2017/src/day12.clj b/2017/src/day12.clj
new file mode 100644
index 0000000..8718bda
--- /dev/null
+++ b/2017/src/day12.clj
@@ -0,0 +1,34 @@
+(ns day12
+  (:require
+   [clojure.string :as str]
+   core
+   input-manager
+   [clojure.set :refer [difference]]))
+
+(def input (->> (input-manager/get-input 2017 12)
+                (map #(str/replace % #"," ""))
+                (map core/split-whitespace)
+                (map (fn [[a _ & rst]]
+                       [(parse-long a) (mapv parse-long rst)]))
+                (into {})))
+
+(defn group-from-start [start]
+  (loop [visited #{}
+         queue [start]]
+    (if-not (seq queue)
+      visited
+      (let [[curr & rst] queue
+            ns (filter (complement visited) (input curr))]
+        (recur (into visited ns)
+               (concat rst ns))))))
+
+;; part one
+(count (group-from-start 0))
+
+;; part two
+(loop [ks (into #{} (keys input))
+       i 0]
+  (if-not (seq ks)
+    i
+    (recur (difference ks (group-from-start (first ks)))
+           (inc i))))