A group of 100 students were surveyed about their favorite sports. Out of the 100 students, 28 students like to play basketball, 31 students like to play badminton, 42 students like to play volleyball, 9 students like to play both basketball and badminton, 10 students like to play basketball and volleyball, 6 students like to play badminton and volleyball, and 4 students like to play the three sports. How many students like to play basketball but not badminton or volleyball?