public class Fraction {
  private int n; // numerator
  private int d; // denominator

  // Constructors
  public Fraction () { // default
    n=0; d=1;	
  }	

  public Fraction (int n, int d) { // with parameters
    this.n = n; // this is the member variable
    this.d = d;
  }

  public Fraction (Fraction toCopy) { // Copy Constructor
    this.n = toCopy.n;
    this.d = toCopy.d;
  }


  // Methods
  
  public void set (int n, int d) {
    this.n = n; this.d = d; 
  }
  
  public Fraction add (Fraction f) {
    n = n*f.d + f.n*d;	
    d = d*f.d; 
    return this; // returns the active instance
  }

  /* implement the missing methods for 
   * subtraction, multiply and divide
   */

  // std method for conversion to string (see API: java.lang.Object)
  public String toString () {
    return ("Fraction("+n+"/"+d+")");
  }
}