class Fraction

public class Fraction {
    private int num;
    private int den;

    public Fraction(){

    }

    public Fraction(int num, int den) {
        this.num = num;
        this.den = den;
    }

    @Override
    public String toString(){
        if (this.den == 1){
            return this.getNum()  + "";
        }
        return this.getNum() + "/" + this.getDen();
    }

    public Fraction multiply(Fraction other){
        int numr = this.getNum() * other.getNum();
        int denr = this.getDen() * other.getDen();
        Fraction res = new Fraction(numr, denr);
        return res;
    }

    public Fraction divide(Fraction other){
        int numr = this.getNum() * other.getDen();
        int denr = this.getDen() * other.getNum();
        Fraction res = new Fraction(numr, denr);
        return res;
    }

    public Fraction sum(Fraction other){
        int numr = this.getNum() * other.getDen() + other.getNum() * this.getDen();
        int denr = this.getDen() * other.getDen();
        Fraction res = new Fraction(numr, denr);
        return res;
    }

    public Fraction substract(Fraction other){
        int numr = this.getNum() * other.getDen() - other.getNum() * this.getDen();
        int denr = this.getDen() * other.getDen();
        Fraction res = new Fraction(numr, denr);
        return res;
    }
    private int gcdByEuclidsAlgorithm(int n1, int n2){
        if(n2 ==0){
            return n1;
        }
        return gcdByEuclidsAlgorithm(n2, n1 % n2);
    }

    public void reduce(){
        int d = gcdByEuclidsAlgorithm(this.num, this.den);
        this.num /= d;
        this.den /= d;
    }


    public int getNum(){
        return this.num;
    }
    public void setNum(int num){
        this.num = num;
    }

    public int getDen() {
        return den;
    }

    public void setDen(int den) {
        if (den != 0) {
            this.den = den;
        }
        else{
            this.den = -1;
            System.out.println("Error!");
        }
    }

}