diff --git a/rot13/solution.md b/rot13/solution.md
index 8ee57ea..305dae2 100644
--- a/rot13/solution.md
+++ b/rot13/solution.md
@@ -5,3 +5,9 @@ One possible approach is to use the `tr` command that translates a set of charac
 Also `sed` has the same ability with the `y` command
 
 ```echo cypher me | sed 'y/abcdefghijklmnopqrstuvwxyz/nopqrstuvwxyzabcdefghijklm/'```
+
+Using the **Character Classes** is possible to avoid writing all the letters of the alphabet and it is also possible to manage easly the case of the character!
+
+```bash
+echo cypher ME | tr a-zA-Z n-za-mN-ZA-N
+```