Решите, пожалуйста, не успеваю.

#include <iostream>
#include <string>
#include <sstream>
using namespace std;
class Fraction {
public:
using value_type = long long;
Fraction(const string& str) {
val = split(str, '/');
normalize();
}
string value() {
return to_string(val.first) + '/' + to_string(val.second);
}
Fraction absolute()const {
return Fraction(abs(val.first), val.second);
}
Fraction& operator-() {
val.first *= -1;
return *this;
}
private:
Fraction(value_type a, value_type b) : val{a, b} {
normalize();
}
pair<value_type, value_type> val;
void normalize() {
auto x = gcd(val);
if (x) {
val.first /= x;
val.second /= x;
if (val.second < 0) {
val.first *= -1;
val.second *= -1;
}
}
}
value_type gcd(pair<value_type, value_type> v) {
v.first = abs(v.first);
if (v.first) {
v.second = abs(v.second);
while (v.first != v.second) {
if (v.first > v.second) swap(v.first, v.second);
v.second -= v.first;
}
}
return v.first;
}
pair<value_type, value_type> split(const string& str, char delim) {
stringstream ss(str);
string token;
pair<value_type, value_type> box;
getline(ss, token, delim);
box.first = stoll(token);
getline(ss, token);
box.second = stoll(token);
return box;
}
friend Fraction operator-(const Fraction& a, const Fraction& b) {
const auto an = a.val.first * b.val.second;
const auto bn = b.val.first * a.val.second;
const auto abn = an - bn;
const auto abd = a.val.second * b.val.second;
return Fraction(to_string(abn) + '/' + to_string(abd));
}
friend bool operator<(const Fraction& a, const Fraction& b) {
return double(a.val.first) / a.val.second < double(b.val.first) / b.val.second;
}
friend bool operator<(const Fraction& a, const double b) {
return double(a.val.first) / a.val.second < b;
}
friend bool operator==(const Fraction& a, const Fraction& b) {
return a.val.first == b.val.first && a.val.second == b.val.second;
}
friend bool operator==(const Fraction& a, const double b) {
return double(a.val.first) / a.val.second == b;
}
friend bool operator>(const Fraction& a, const Fraction& b) {
return double(a.val.first) / a.val.second > double(b.val.first) / b.val.second;
}
friend bool operator>(const Fraction& a, const double b) {
return double(a.val.first) / a.val.second > b;
}
friend Fraction operator%(const Fraction& a, const Fraction& b) {
auto xa = a.absolute();
auto xb = b.absolute();
if (xa < xb) return a;
auto x = xa - xb;
if (x == 0) return Fraction(0, 1);
while (x > b) x = x - b;
return a.val.first > 0? x : -x;
}
};
int main() {
string a, b;
cin >> a >> b;
Fraction fa(a), fb(b);
auto fc = fa % fb;
cout << fc.value() << '\n';
system("pause > nul");
}