How to retrieve existing user password in Oracle Database 19c Enterprise Edition Release 19.0.0.0.0

forgot user password, how can retrieve user UNENCRYPTED password in Oracle 19c?

mange to retrieve encrypted password using below SQL. But need unencrypted

with t as (select dbms_metadata.get_ddl('USER','USER_NAME') ddl from dual )

   select replace(substr(ddl,1,instr(ddl,'DEFAULT')-1),'CREATE','ALTER')||';'

    from t;