diff --git a/README.md b/README.md
index 66370ab..37b1990 100644
--- a/README.md
+++ b/README.md
@@ -41,3 +41,4 @@
 15 - 59 = -44
 15 * 52 = 780
 72 * 10 = 720
+81 - 77 = 4