15/5/c

#include <iostream>
#include <windows.h>

using namespace std;

const int maxSize = 16;
const int maxVal = 32767;

int takeIntValue(int max, int min) {
    int length;
    bool isCorrect;
    do {
        isCorrect = true;
        try {
            cin >> length;
            if (cin.fail()) throw 1;
            if (length > max || length < min) throw 2;
        }
        catch (int exc) {
            if (exc == 1) {
                cin.clear();
                cin.ignore(32767, '\n');
                isCorrect = false;
                cout << "Введено недопустимое значение!";
            }
            else {
                isCorrect = false;
                cout << "Введено значение, выходящее за пределы!";
            }
        }
    } while (!isCorrect);
    return length;
}
bool checkContract(int num, int denom) {
    bool isContract = false;
    int i = 2;
    if (num > denom || (num < 0 && denom < 0))
        isContract = true;
    while (!isContract && i <= sqrt(denom)) {
        if (num % i == 0 && denom % i == 0)
            isContract = true;
        i++;
    }
    return isContract;
}
class fraction{
    protected:
        int numerator = 0;
        int denominator = 0;
    public:
        friend fraction operator + (fraction frac1, fraction frac2);
        friend fraction operator * (fraction frac1, fraction frac2);
        friend istream& operator >> (istream &cin, fraction &frac);
        friend ostream& operator << (ostream &cout, fraction frac);
        void contract() {
            if (numerator < 0 && denominator < 0) {
                numerator *= -1;
                denominator *= -1;
            }
            int i = 2;
            while (i <= sqrt(denominator)) {
                if (numerator % i == 0 && denominator % i == 0) {
                    numerator /= i;
                    denominator /= i;
                }
                i++;
            }
        }
};
istream& operator >> (istream &cin, fraction &frac) {
    bool isCorrect;
    do {
        isCorrect = true;
        cout << "Введите числитель: ";
        frac.numerator = takeIntValue(maxVal, -maxVal);
        cout << "Введите знаменатель: ";
        frac.denominator = takeIntValue(maxVal, -maxVal);
        if (checkContract(frac.numerator, frac.denominator)) {
            cout << "Дробь не соответствует условию!\n";
            isCorrect = false;
        }
    } while (!isCorrect);
    return cin;
}
ostream& operator << (ostream &cout, fraction frac) {
    cout << frac.numerator << "/" << frac.denominator;
    return cout;
}
fraction operator + (fraction frac1, fraction frac2) {
    if (frac1.denominator != frac2.denominator) {
        frac1.numerator *= frac2.denominator;
        frac2.numerator *= frac1.denominator;
        frac1.numerator += frac2.numerator;
        frac1.denominator *= frac2.denominator;
    }
    else {
        frac1.numerator += frac2.numerator;
    }
    frac1.contract();
    return frac1;
}
fraction operator * (fraction frac1, fraction frac2) {
    frac1.numerator *= frac2.numerator;
    frac1.denominator *= frac2.denominator;
    frac1.contract();
    return frac1;
}
int main() {
    SetConsoleOutputCP(1251);
    fraction fract1, fract2;
    cout << "Заполните первую дробь.\n";
    cin >> fract1;
    cout << "Заполните вторую дробь.\n";
    cin >> fract2;
    cout << "Сумма дробей равна " << fract1 + fract2 << endl;
    cout << "Произведение дробей равно " << fract1 * fract2;
}