friend and nested classes

[Chameleon]

How can I make the following code to compile?
---------------------------------------------
class A
{
class B
{
int a;
friend class A;
friend class C;
};

class C
{
C() { B b; b.a = 1000; }
};

A() { B b; b.a = 1000; }
};

int main() { return 0; }

 

[Chameleon]

O/H Chameleon Ýãñáøå:

How can I make the following code to compile?

class C; // ok now!