The following story is from N. Wirth's (1976) "Algorithms + Data Structures = programs". "I married a widow (let's call her W) who has a grown up daughter (let's call her D). My father (F), who visited us quite often, fell in love with my step daughter and married her. Hence my father became my son in law and my step daughter became my mother. Some months later my wife gave birth to a son (S1) who became the brother in law of my father, as well as my uncle. The wife of my father, that is, my step daughter, also had a son (S2). "
Express the facts and rules of the above story in CNF (conjunctive normal form) and derive the conclusion that "I am my own grandfather" using resolution as a rule of inference.