#include <vector>
#include <iostream>

using namespace std;

class Behaviour
{
public:
    Behaviour() = default;
    virtual ~Behaviour() = default;

    virtual int apply(int target) const = 0;
};

class Square : public Behaviour
{
public:
    int apply(int target) const override
    {
        return target * target;
    }
};

class Add : public Behaviour
{
public:
    Add(int value)
        : value {value}
    {}

    int apply(int target) const override
    {
        return target + value;
    }
private:
    int value;
};

int apply_behaviour(int value, Behaviour const& behaviour)
{
    return behaviour.apply(value);
}

int main()
{   
    int value{0};

    Add a1{3};
    Square s1{};
    Add a2{1};
    Square s2{};

    value = apply_behaviour(value, a1);
    value = apply_behaviour(value, s1);
    value = apply_behaviour(value, a2);
    value = apply_behaviour(value, s2);

    std::cout << value << std::endl;
    return 0;
}