diff --git a/2021/README.md b/2021/README.md
index e9e1649..e3448af 100644
--- a/2021/README.md
+++ b/2021/README.md
@@ -16,7 +16,7 @@
 | :-: | :-: | :-: | :-: | :-: | :-:  | :-: |
 |     |     |     | [1] | [2] | [3]  | [4] |
 | [5] | [6] | [7] | [8] | [9] | [10] | [11]|
-| [12]| [13]| [14]| [15]  | [16]  | [17]   | 18  |
+| [12]| [13]| [14]| [15]  | [16]  | [17]   | [18]  |
 | 19  | 20  | 21  | 22  | 23  | 24   | 25  |
 
 <!-- links -->
@@ -38,3 +38,4 @@
 [15]: ./lib/2021/15.ex
 [16]: ./lib/2021/16.ex
 [17]: ./lib/2021/17.ex
+[18]: ./lib/2021/18.ex
diff --git a/2021/lib/2021/18.ex b/2021/lib/2021/18.ex
index 12303ff..c7ae6f4 100644
--- a/2021/lib/2021/18.ex
+++ b/2021/lib/2021/18.ex
@@ -10,6 +10,15 @@ aoc 2021, 18 do
   end
 
   def p2 do
+    numbers = input() |> Enum.to_list()
+
+    for a <- numbers, b <- numbers, a != b do
+      concat(a, b)
+      |> reduce()
+      |> to_lists()
+      |> magnitude()
+    end
+    |> Enum.max()
   end
 
   def magnitude([a, b]) do