Displaying text when the user input invalid but continuing when it is valid

Question

Whenever exercise_type is not one of the options in the table, display "Invalid type of exercise" in the output/console screen instead. Whenever difficulty_level is not one of the options in the table, display "Invalid difficulty level" in the output/console screen instead. Concept(s) to Apply:

1. Nested if/elif/else
2. int()
3. input()
4. Variables
5. print()

This is part of my whole assignment but im having trouble doing this using only these concepts. There are 4 exercise types (arms, legs, core, yoga) and 4 difficulty levels (1,2,3,4) But I cannot figure out how to do this. I am very much new to coding. The tables are already completed and they display properly but I am stuck here.