Simplify the following text for a Grade 7 native English-speaking person.
Original: FranÃ ois Duvalier ( 14 April 1907 - 21 April 1971 ) , known as `` Papa Doc '' , was the President ( dictator ) and Head of State of Haiti from 1957 until his death .
Simplified: FranÃ ois Duvalier ( April 14 , 1907 - April 21 , 1971 ) was the President of Haiti from 1957 until his death in 1971 .