diff --git a/Algo/Courses/Chapter 6 - Lists (Exercises).md b/Algo/Courses/Chapter 6 - Lists (Exercises).md
index 0d563cc..4bc0b66 100644
--- a/Algo/Courses/Chapter 6 - Lists (Exercises).md	
+++ b/Algo/Courses/Chapter 6 - Lists (Exercises).md	
@@ -266,3 +266,13 @@ let assoc k l =
 			in findkey l;;
 val assoc: int -> (int * 'a)list -> 'a = <fun>
 ```
+
+## Exercise 5.2
+```Ocaml
+let rec flattten = function
+	| [] -> []
+	| e::t -> (match e with
+		| [] -> flatten t
+		| e2::t2 -> e2==flatten(2::t));;
+
+val flatten: 'a list list -> 'a list = <fun>