В классе нужно переделать методы на виртуальные

#include <iostream>
#include <cmath>
#include <string>
using namespace std;
 
 
//------------
class praktika {
 
public:
    praktika(std::string name, std::string last_name, std::string otestvo_name, double year, double month, double day, double year1, double month1, double day1, double year2, double month2, double day2) {
        name_ = name;
        last_name_ = last_name;
        otestvo_name_ = otestvo_name;
        year_ = year;
        month_ = month;
        day_ = day;
        year1_ = year1;
        month1_ = month1;
        day1_ = day1;
        year2_ = year2;
        month2_ = month2;
        day2_ = day2;
    }
    void Set_snils(std::string name, std::string last_name, std::string otestvo_name, double year, double month, double day, double year1, double month1, double day1, double year2, double month2, double day2);
    std::string Get_name();
    std::string Get_last_name();
    std::string Get_otestvo_name();
    void age(double year, double month, double day, double year1, double month1, double day1, double year2, double month2, double day2);
 
private:
    std::string name_;
    std::string last_name_;
    std::string otestvo_name_;
    double year_;
    double month_;
    double day_;
    double year1_;
    double month1_;
    double day1_;
    double year2_;
    double month2_;
    double day2_;
    double res;
    double res1;
};
 
 
 
std::string praktika::Get_name() {
 
    return name_;
}
 
std::string praktika::Get_last_name() {
 
    return last_name_;
}
 
std::string praktika::Get_otestvo_name() {
 
    return otestvo_name_;
}
 
void praktika::Set_snils(std::string name, std::string last_name, std::string otestvo_name, double year, double month, double day, double year1, double month1, double day1, double year2, double month2, double day2) {
    name_ = name;
    last_name_ = last_name;
    otestvo_name_ = otestvo_name;
    year_ = year;
    month_ = month;
    day_ = day;
    year1_ = year1;
    month1_ = month1;
    day1_ = day1;
    year2_ = year2;
    month_ = month;
    day2_ = day2;
}
void praktika::age(double year, double month, double day, double year1, double month1, double day1, double year2, double month2, double day2) {
 
    setlocale(LC_ALL, "Russian");
 
    if ((month1 < month) || ((month1 = month) && (day1 <= day)))
        res = year - year1;
    else res = year - year1 - 1;
    if ((month1 < month2) || ((month1 = month2) && (day1 <= day2)))
        res1 = year2 - year1;
    else res1 = year2 - year1 - 1;
 
    std::cout << "Вам " << res << " лет" << endl;
    std::cout << "на текущую дату Вам " << res1 << " лет" << endl;
}
 
 
int main() {
    setlocale(LC_ALL, "rus");
    std::string name, last_name, otestvo_name;
    double year, month, day, year1, month1, day1, year2, month2, day2;
    std::cout << "Имя: ";
    std::cin >> name;
 
    std::cout << "Фамилия: ";
    std::cin >> last_name;
 
    std::cout << "Отчество: ";
    std::cin >> otestvo_name;
 
    std::cout << "Сегодняшний день: ";
    std::cin >> day;
 
    std::cout << "Сегодняшний месяц: ";
    std::cin >> month;
 
    std::cout << "Сегодняшний год: ";
    std::cin >> year;
 
    std::cout << "день рождения: ";
    std::cin >> day1;
 
    std::cout << "месяц рождения: ";
    std::cin >> month1;
 
    std::cout << "год рождения: ";
    std::cin >> year1;
 
    std::cout << "указанный день: ";
    std::cin >> day2;
 
    std::cout << "указанный месяц: ";
    std::cin >> month2;
 
    std::cout << "указанный год: ";
    std::cin >> year2;
 
    praktika triangle(name, last_name, otestvo_name, year, month, day, year1, month1, day1, year2, month2, day2);
    std::cout << "--------------\n"
        "ФИО = " << triangle.Get_name() << " " <<
        triangle.Get_last_name() << " " <<
        triangle.Get_otestvo_name() << "\n" <<
        "Фамилия.И.О. = " << triangle.Get_name() << " " <<
        triangle.Get_last_name()[0] << "." <<
        triangle.Get_otestvo_name()[0] << ".\n";
    triangle.age(year, month, day, year1, month1, day1, year2, month2, day2);
    system("pause");
    return(0);
}