class rational
{
    public int n, d;   //numerator and denominator

    public rational(int a, int b) {n=a; d=b;}  // constructor
    
    public boolean equals(rational B) // compare B with this rational
    { return n*B.d == d*B.n; }

    public rational mult(rational B) // multiply B and this rational
    { return new rational(n*B.n, d*B.d); }

    public rational add(rational B)  // add B to this rational
    {
	int a = n*B.d + d*B.n;
	int b = d*B.d;
	return new rational(a,b);
    }

    public void invert() // invert the fraction destructively
    { int temp = n; n=d; d=temp; }

    public String toString() { return n+"/"+d; }  // output

} // class rational

public class userationals
{
    public static void main(String[] args)
    {
	rational A = new rational(1,2);
	rational B = new rational(2,3);
	System.out.println(A.mult(B));
	System.out.println(A.equals(new rational(2,4)));
	rational C = new rational(1,0);
    }
}