#include <iostream>
using namespace std;

class a
{


public:
    a(void)
    {
        cout<<"a defaut ctor"<<endl;
    }
    a(int i)
    {
        cout<<"a custom ctor "<<i<<endl;
    }
};
class b : public a
{
public:
    b(void)
    {
        cout<<"b defaut ctor"<<endl;
    }
    b(int i) : a(i)
    {
        cout<<"b custom ctor "<<i<<endl;
    }
};

int main()
{
    b B1;
    b B2(5);

    return 0;
}