Difference of Squares Input Validation

[bushidocodes]

The difference of squares spec should validate that the parameter is a natural number. It should be sufficient to return -1 in case of error.

[keiravillekode]

There is nothing specifying that the input i32 are signed. If the solution considers them unsigned, the only non-natural number is 0. It would be reasonable to return 0 (or a negative to report error) in this case.

We can consider error checking to be out of scope for this exercise. There are already large i32 values that can't give valid results as the results would not fit in an i32. We are not asking students to detect and reject these values.