#include <cstdio>
int main() {  
   class T1;
   class T2;
   class T1{
   public:
      int a;
      T2* tu;
   };
   class T2{
   public:
      T1* mu;
   };
   
   T1 a1;
   T2 a2;
   a1.a=17;
   a1.tu=&a2;
   a2.mu=&a1;
   printf("%d %d\n",a1.a,a1.tu->mu->a);
}