diff --git a/hws/04_ride_sharing/README.md b/hws/04_ride_sharing/README.md
index 1aaf9d4..f764f1a 100644
--- a/hws/04_ride_sharing/README.md
+++ b/hws/04_ride_sharing/README.md
@@ -143,7 +143,7 @@ Here
 - output0.txt is the output file where you print messages to user or driver.
 - output1.txt is the output file where you print the updated drivers information.
 - output2.txt is the output file where you print the updated users information.
-- phoneNumber will be corresponding to one of the users in the users.txt whose state is "Ready_to_request".
+- phoneNumber. Ideally this should be a phone number which corresponds to one of the users in the users.txt whose state is "Ready_to_request"; but life is not always ideal, and how your program should cope with various phone number cases will be described in this section.
 - request indicates this is a ride request.
 
 When this command is run, and