The grammar of natural languages such as English exhibits a recursive structure. This structure can be expressed in syntax rules written in the format known as BNF (Bachus-Naur Form, named after the people who invented it). You have probably seen BNF used to specify the syntax of programming languages. While BNF is ordinarily used as a guide for parsing (that is, determining whether and how a given string follows the syntax rules), it can also be used a guide for generating strings that follow the syntax rules.

Write program that implements the following rules:

::= [ ]

::=

::= |

[ ]. [ who ]

::= |

|

is |

believes that

::= and | or | but | because

::= Fred | Jane | Richard Nixon | Miss America

::= man | woman | fish | elephant | unicorn

::= a | the | every | some

::= big | tiny | pretty | bald

::= runs | jumps | talks | sleeps

::= loves | hates | sees | knows | looks for | finds