diff --git a/lab03/kvtree.ml b/lab03/kvtree.ml
new file mode 100644
index 0000000..fa99d34
--- /dev/null
+++ b/lab03/kvtree.ml
@@ -0,0 +1,72 @@
+type ('k, 'v) kvtree = Leaf | Node of 'k * 'v * ('k, 'v) kvtree * ('k, 'v) kvtree;;
+
+let rec kvtree_size t =
+  match t with
+  | Leaf -> 0
+  | Node (_, _, l, r) ->
+    1 + kvtree_size l + kvtree_size r;;
+
+let rec kvtree_height t =
+  match t with
+  | Leaf -> 0
+  | Node (_, _, l, r) ->
+    1 + max (kvtree_height l) (kvtree_height r);;
+
+let kvtree_empty = Leaf;;
+
+let kvtree_is_empty t = t = Leaf;;
+
+let rec kvtree_insert ~cmp k v t =
+  match t with
+  | Leaf -> Node (k, v, Leaf, Leaf)
+  | Node (k', v', l, r) when cmp k k' < 0 ->
+    Node (k', v', kvtree_insert ~cmp k v l, r)
+  | Node (k', v', l, r) when cmp k k' > 0 ->
+    Node (k', v', l, kvtree_insert ~cmp k v r)
+  | _ -> t;;
+
+let kvtree_of_list ~cmp l =
+  List.fold_left (fun acc (k, v) -> kvtree_insert ~cmp k v acc) Leaf l;;
+
+let rec kvtree_mem ~cmp k t =
+  match t with
+  | Leaf -> false
+  | Node (k', _, l, _) when cmp k k' < 0 ->
+    kvtree_mem ~cmp k l
+  | Node (k', _, _, r) when cmp k k' > 0 ->
+    kvtree_mem ~cmp k r
+  | _ -> true;;
+
+let rec kvtree_largest t =
+  match t with
+  | Leaf -> failwith "kvtree_largest: empty tree"
+  | Node (k, v, _, Leaf) -> (k, v)
+  | Node (_, _, _, r) -> kvtree_largest r;;
+
+let rec kvtree_smallest t =
+  match t with
+  | Leaf -> failwith "kvtree_smallest: empty tree"
+  | Node (k, v, Leaf, _) -> (k, v)
+  | Node (_, _, l, _) -> kvtree_smallest l;;
+
+let rec kvtree_delete ~cmp k t =
+  match t with
+  | Leaf -> Leaf
+  | Node (k', v, l, r) when cmp k k' < 0 ->
+    Node (k', v, kvtree_delete ~cmp k l, r)
+  | Node (k', v, l, r) when cmp k k' > 0 ->
+    Node (k', v, l, kvtree_delete ~cmp k r)
+  | Node (_, _, l, Leaf) -> l
+  | Node (_, _, Leaf, r) -> r
+  | Node (_, _, l, r) ->
+    let (ks, vs) = kvtree_largest l in
+    Node (ks, vs, kvtree_delete ~cmp ks l, r);;
+
+let rec kvtree_find_opt ~cmp k t =
+  match t with
+  | Leaf -> None
+  | Node (k', _, l, _) when cmp k k' < 0 ->
+    kvtree_find_opt ~cmp k l
+  | Node (k', _, _, r) when cmp k k' > 0 ->
+    kvtree_find_opt ~cmp k r
+  | Node (_, v, _, _) -> Some v;;
diff --git a/lab03/part1.ml b/lab03/part1.ml
new file mode 100644
index 0000000..f5aa132
--- /dev/null
+++ b/lab03/part1.ml
@@ -0,0 +1,9 @@
+let digits n =
+  let rec digits' n acc =
+    if n = 0 then acc
+    else digits' (n / 10) (n mod 10 :: acc)
+  in
+  digits' n [];;
+
+let int_of_digits d =
+  (List.fold_left (fun x acc -> (x + acc) * 10) 0 d) / 10;;