1 #include <iostream>
 2 
 3 using namespace std;
 4 
 5 class Trapezium
 6 {
 7     private:
 8         int x1,y1,x2,y2,x3,y3,x4,y4;
 9     public:
10         void initial(){x1=0,x2=0;x3=0;x4=0;y1=0;y2=0;y3=0;y4=0;return;}
11         void GetPosition(int&,int&,int&,int&,int&,int&,int&,int&);
12         void Area()
13         {
14             double s;
15             s=((x2-x1)+(x4-x3))*(y2-y4)/2.0;
16             cout<<s<<endl;
17             return;
18         }
19 };
20 
21 void Trapezium::GetPosition(int& a,int& b,int& c,int& d,int& e,int& f,int& g,int& h)
22 {
23     x1=a;y1=b;x2=c;y2=d;x3=e;y3=f;x4=g;y4=h;
24     return;
25 }
26 
27 int main()
28 {
29     int x[4],y[4];
30     Trapezium one;
31     for(int i=0;i<4;i++)    cin>>x[i]>>y[i];
32     one.initial();
33     one.GetPosition(x[0],y[0],x[1],y[1],x[2],y[2],x[3],y[3]);
34     one.Area();
35     return 0;
36 }