Trick C++ Question

trick.cpp

#include <iostream>
using namespace std;

class Base
{
    int _value;

public:
    Base()
    {
        _value = GenerateValue();
    }
    
    virtual int GenerateValue()
    {
        return 1;
    }
    
    int GetValue()
    {
        return _value;
    }
};

class Derived : public Base
{
public:
    virtual int GenerateValue()
    {
        return 2;
    }
};

int main()
{
    Derived d;
    cout << d.GetValue() << endl;
    return 0;
}