How to drop the database in oracle?

SQL> --How to drop the database?--
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup restrict mount;
ORACLE instance started.

Total System Global Area 1824624640 bytes
Fixed Size                  1337184 bytes
Variable Size            1090521248 bytes
Database Buffers          721420288 bytes
Redo Buffers               11345920 bytes
Database mounted.
SQL> drop database;

Database dropped.

Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL>