class rational {

   private int numerator;
   private int denominator;

   public rational (int a, int b) {

     numerator = a; 
     denominator = b;
   }

   public rational sum (rational r) {

     int num, den;
     den = denominator * r.get_denominator();
     num = numerator * r.get_denominator() + r.get_numerator() * denominator;

     return new rational (num, den);
   }

   public int get_numerator() { return numerator; }

   public int get_denominator() { return denominator; }

   public String str () { return numerator + "/" + denominator; }

   public void reduce() {

      int factor;
      factor = gcd(numerator, denominator);
      numerator = numerator / factor;
      denominator = denominator / factor;
   }

   private int gcd (int x, int y) {

      int t;
      while (y>0) {
        t = x % y;
        x = y;
        y = t;
      }
      return x;
   }

}