// This program uses virtual base classes.
#include <iostream>
using namespace std;

class base {
public:
  int i;
};

// derived1 inherits base as virtual.
class derived1 : virtual public base {
public:
  int j;
};

// derived2 inherits base as virtual.
class derived2 : virtual public base {
public:
  int k;
};

/* derived3 inherits both derived1 and derived2.
   This time, there is only one copy of base class. */
class derived3 : public derived1, public derived2 {
public:
  int sum;
};

int main()
{
  derived3 ob;

  ob.i = 10;  // now unambiguous
  ob.j = 20;
  ob.k = 30;

  // unambiguous
  ob.sum = ob.i + ob.j + ob.k;

  // unambiguous
  cout << ob.i << " ";

  cout << ob.j << " " << ob.k << " ";
  cout << ob.sum;

  return 0;
}