diff --git a/main.roc b/main.roc
index b264780..793071a 100644
--- a/main.roc
+++ b/main.roc
@@ -10,6 +10,13 @@ addAndStringify = \num1, num2 ->
     else
         Num.toStr sum
 
+calcFac = \number ->
+if number == 0 then
+    1
+else 
+    (number * (calcFac (number - 1)))
+
 main =
     Stdout.line! "I'm a Roc application!"
     Stdout.line! (addAndStringify 2 3)
+    Stdout.line! (Num.toStr (calcFac 10))