Is it an One-to-One function?
Is it an Onto function?

We set the domain and range of function f, in [0, 1, 2, 3, 4, 5].

1. Define a function, f, to take an integer, x, from callers and
   return (4 * x) % 6 to the callers.
2. In the main() function, you have two choices to define the domain
   in the list, [0, 1, 2, 3, 4, 5].
   • Use a loop to do the work:
     Start an argument of 0 to call function f, and print the returning value.
     After that increase the argument by 1 to call function f and print the
     returning value. Keep doing the same work until the argument is 5.
   • Go ahead to print two columns which one is x and the other is f.
     print the results 6 times one by one.