num gcf(num a, num b)
Returns the greatest common factor of two numbers.
The result will be negative if one or both arguments are negative.
gcf(18, 24) -> 6 gcf(-18, 24) -> -6 gcf(18, -24) -> -6 gcf(-18, -24) -> -6 gcf(18.0, 24.0) -> 6.0 gcf(-18.0, 24.0) -> -6.0 gcf(18.0, -24.0) -> -6.0 gcf(-18.0, -24.0) -> -6.0