main creates a Fraction with no arguments – and this class doesn’t compile, because it only defines a
two-argument constructor. Submit it as-is and read the error before fixing anything.
This is the “quiet trap” from the lesson made concrete: writing the (int, int) constructor took away the free
default constructor C++ would otherwise have generated. Add a Fraction() constructor of your own, initializing
numerator to 0 and denominator to 1, so both ways of creating a Fraction work.