context: Eton has a long list of distinguished former pupils. David Cameron is the 19th British prime minister to have attended the school, and has recommended that Eton set up a school in the state sector to help drive up standards. Eton now co-sponsors a state sixth-form college in Newham, a deprived area of East London, called the London Academy of Excellence, opened in 2012, which is free of charge and aims to get all its students into higher education. In September 2014, Eton opened, and became the sole educational sponsor for, a new purpose-built co-educational state boarding and day school for around 500 pupils, Holyport College, in Maidenhead in Berkshire, with construction costing around £15 million, in which a fifth of places for day pupils will be set aside for children from poor homes, 21 boarding places will go to youngsters on the verge of being taken into care, and a further 28 boarders will be funded or part-funded through bursaries.
question: ఎన్ని మంది బ్రిటిష్ ప్రధానులు ఈటన్ సమావేశానికి హాజరయ్యారు?
answers: 19