#include <iostream>
#include <vector>
#include <string>
#include <memory>
#include <algorithm>

class Person {
public:
    Person(int id, std::string name)
        : id_(id), name_(std::move(name)) {}

    int id() const { return id_; }
    const std::string& name() const { return name_; }

    virtual void greet() const {
        std::cout << "Hello, I'm " << name_ << std::endl;
    }

    virtual ~Person() = default;

private:
    int id_;
    std::string name_;
};

class Student : public Person {
public:
    Student(int id, std::string name, double gpa)
        : Person(id, std::move(name)), gpa_(gpa) {}

    void greet() const override {
        std::cout << "Hi, I'm " << name() << " (GPA: " << gpa_ << ")" << std::endl;
    }

private:
    double gpa_;
};

template <typename T>
T max_value(T a, T b) {
    return (a > b) ? a : b;
}

int main() {
    auto p = std::make_unique<Student>(1, "Alice", 3.9);
    p->greet();

    std::vector<int> nums = {3, 1, 4, 1, 5, 9};
    std::sort(nums.begin(), nums.end());

    for (int n : nums) {
        std::cout << n << " ";
    }
    std::cout << std::endl;

    std::cout << "Max of 10 and 20: " << max_value(10, 20) << std::endl;
    return 0;
}