class Rational {
	Rational(num, den) {
		this.num = num;
		this.den = den;
	}

	public String toString() {return num + "/" + den;}

	static Rational read(Scanner scanner) {
		if (!scanner.hasNextInt()) return null;
		int num = scanner.nextInt();
		int den = scanner.nextInt();
		return new Rational(num, den);
	}

	int num, den;
}