начал рациональные дроби

#include <algorithm>
#include <cmath>
#include <iostream>
#include <map>
#include <set>
#include <string>
#include <utility>
#include <vector>
#include <numeric>

using namespace std;
/*int gcd(int n, int m) {
    return 2;
}*/


class Rational {
public:
    int Numerator() const {
        return numerator_;
    }

    int Denominator() const {
        return denominator_;
    }
    Rational() {
        Numerator();
        Denominator();
    }
    Rational(int i) {
        SetNum(i);
        SetDen(1);
    }
    Rational(int i, int j) {
        int c=1;
        if (i!=0)
        {
        c = gcd(abs(i),abs(j));
        }
        if (i*j<0) {
            i=-abs(i);
            j=abs(j);
            }
        if (i*j>0){
            i=abs(i);
            j=abs(j);
        }
     //   cout<<"***"<<i<<"***"<<j<<"***"<<c<<"***"<<endl;
        SetNum(i/c);
        SetDen(j/c);
    }

private:
    int numerator_ = 0;
    int denominator_ = 1;

    void SetNum(int num) {
        numerator_ = num;
    }
    void SetDen(int den) {
        denominator_ = den;
    }

};
Rational Add(Rational r1, Rational r2) {
    int numerator = r1.Numerator() * r2.Denominator() + r2.Numerator() * r1.Denominator();
    int denominator = r1.Denominator() * r2.Denominator();
    // Создаём и возвращаем дробь с заданным числителем и знаменателем
    return Rational{ numerator, denominator };
}

int main() {
    Rational r1;
    Rational r2(8);
    Rational r3(-8);
    Rational r4(1,2);
    Rational r5(-1,2);
    Rational r6(10,-20);
    Rational r7(-1,-2);
    Rational r8(10,15);
    Rational r9(0,-5);
    cout << r1.Numerator() << "/" << r1.Denominator()<<endl;
    cout << r2.Numerator() << "/" << r2.Denominator()<<endl;
    cout << r3.Numerator() << "/" << r3.Denominator()<<endl;
    cout << r4.Numerator() << "/" << r4.Denominator()<<endl;
    cout << r5.Numerator() << "/" << r5.Denominator()<<endl;
    cout << r6.Numerator() << "/" << r6.Denominator()<<endl;
    cout << r7.Numerator() << "/" << r7.Denominator()<<endl;
    cout << r8.Numerator() << "/" << r8.Denominator()<<endl;
    cout << r9.Numerator() << "/" << r9.Denominator()<<endl;

    /* Rational zero;     // Дробь 0/1 = 0
    const Rational seven(7); // Дробь 7/1 = 7
    const Rational one_third(1, 3); // Дробь 1/3
    vector<Rational> numbers;
    numbers.push_back(Rational{ 7, 8 });
    // Следующие 2 строки эквивалентны - добавляют в numbers дробь 3/1
    numbers.push_back(Rational{ 3 });
    numbers.push_back(3);
    Rational sum = Add(Rational{ -1,6 }, one_third);
    // Выведет 1/2
    cout << sum.Numerator() << "/" << sum.Denominator();

    */