#include<iostream.h> 
#include<math.h> 
class Triangle 
{ 
  int x,y,z; 
  double area; 
public: 
  Triangle(int i,int j,int k) 
  { 
   double s; 
   x=i;y=j;z=k; 
   s=(x+y+z)/2.0; 
   area=sqrt(s*(s-x)*(s-y)*(s-z)); 
  } 
  void disparea() 
  { 
   cout<<"Area="<<area<<endl; 
  } 
  friend double operator+(Triangle t1,Triangle t2) 
  { 
   return t1.area+t2.area; 
  } 
  friend double operator+(double d,Triangle t) 
  { 
   return d+t.area; 
  } 
}; 
void main() 
{ 
Triangle t1(3,4,5),t2(4,5,6),t3(5,6,7),t4(6,7,8); 
double s; 
cout<<"t1:"; t1.disparea(); 
cout<<"t2:"; t2.disparea(); 
cout<<"t3:"; t3.disparea(); 
cout<<"t4:"; t4.disparea(); 
s=t1+t2+t3+t4; 
cout<<"總面積="<<s<<endl; 
}