diff --git a/4/prompt.md b/4/prompt.md
index 5ec1aee..dd204a6 100644
--- a/4/prompt.md
+++ b/4/prompt.md
@@ -1,4 +1,4 @@
-# Here is what I prompted OpenAI with to get day4-by-ai.c and day4.by.ai.s:
+# Here is what I prompted OpenAI with to get day4-by-ai.c and day4-by-ai.s:
 consider a text file like this:
 22-65,22-66
 91-94,63-91