#include <iostream>
#include <list>
#include <algorithm>
 
using namespace std;
 
template< typename T >
class Rect{
protected:
  T width, height;
public:
  Rect(T a, T b){
    width = a;
    height = b;
  }
  template< typename U >
  Rect(Rect<U> const &r){
    width = r.width;
    height = r.height;
  }
  int area(){
    return width*height;
  }
 
  template <typename U> friend class Rect;
};
 
int main(){
  Rect<int> a(3,4);
  Rect<float> b(a);
  cout<<b.area()<<endl;
}

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