Teacher:In this task, you are given an input list A. You need to extract and sort the unique digits used in the list in ascending order. Return -1 if there is no digit in the list.
Teacher: Now, understand the problem? Solve this instance: ['273', '203', '337', 'q', 'l', 'm', '213', '71']
Student:
0, 1, 2, 3, 7