Read the passage below and solve the questions based on it.
In a class of 106 students, each student studies at least one of the three subjects maths, political science and chemistry. 48 of them study maths, 51 political science and 53 chemistry. 16 study maths and political science, 17 study maths and chemistry and 18 study political science and chemistry.
The number of students who study exactly one subject is