#include <iostream>
using namespace std;
 
class A {
public:
    A() { cout << "A"; }
    A(const A&) { cout << "a"; }
};
 
class B : public virtual A {
public:
    B() { cout << "B"; }
    B(const B &b) : A(b) { cout << "b"; }
};
 
class C : public virtual A {
public:
    C() { cout << "C"; }
    C(const C &c) : A(c) { cout << "c"; }
};
 
class D : public B, C {
public:
    D() { cout << "D"; }
    D(const D &d) : A(d), B(d), C(d) { cout << "d"; }
};
 
int main()
{
    D d;
	D d2{d}; // or: D d2 = d;
    return 0;
}

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