diff --git a/README.md b/README.md
index 25732d8..5bd2a58 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@ C code for videos on YouTube Channel https://www.youtube.com/c/NilsBerglund
 
 Parameter values used in specific simulations will be gradually added to file `Parameters.md`, `Parameters_June21.md` and so on.
 
-There are two groups of 4 files and 8 files:
+There are two groups of 4 files and 9 files:
 
 ### Simulations of classical particles in billiards.