How could I fix this warning? SQL*Plus: Release 12.2.0.1.0 Production on Thu Sep 20 13:08:07 2018

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Enter user-name: system
Enter password:
ERROR:
ORA-28002: the password will expire within 4 days



Every time I login into my database it shows this warning message of password gonna expire in .. days. Now its just 4 days left I don't know what to do to fix this warning.
Use the password command after logging in to change your password:

SQL&gt; password
Changing password for SYSTEM
Old password:
New password:
Retype new password:
Password changed
SQL&gt;