Класс "Продукт", вычисление общей калорийности продукта

#include <iostream>
 
class Product
{
private:
    unsigned int first;
    double second;
public:
    Product(int m_first, int m_second) : first(m_first), second(m_second) {}
 
    friend std::ostream& operator <<(std::ostream&, Product&);
};
 
std::ostream& operator <<(std::ostream &os, Product &a)
{
    float sum{a.second * 1000 / 100};
    return os << sum;
}
 
int main()
{
    unsigned int first;
    int second;
    std::cout << "First: ";
    std::cin >> first;
    std::cout << "Second: ";
    std::cin >> second;
    Product newproduct(first, second);
    std::cout << newproduct;
    return 0;
}

float sum{a.second * 1000 / a.first};

#include <iostream>
 
class Product
{
private:
    unsigned int first;
    double second;
public:
    Product(int m_first, int m_second) : first(m_first), second(m_second) {}
 
    friend std::ostream& operator <<(std::ostream&, Product&);
};
 
std::ostream& operator <<(std::ostream &os, Product &a)
{
    float sum{a.second*10 * a.first};
    return os << sum;
}
 
int main()
{
    unsigned int first;
    int second;
    std::cout << "kilokalorii: ";
    std::cin >> first;
    std::cout << "Massa: ";
    std::cin >> second;
    Product newproduct(first, second);
    std::cout << newproduct;
    return 0;
}