1 #include <iostream>
 2 #include <cmath>
 3 #include"iomanip"
 4  
 5 using namespace std;
 6  
 7 struct Point
 8 {
 9     char color;
10     int x;
11     int y;
12     int z;
13 };
14 //求三角形面積;
15 //返回-1為不能組成三角形;
16 double count_triangle_area(Point a,Point b,Point c){
17     double area = -1
 
;
18  
19     double side[3];//儲存三條邊的長度;
20  
21     side[0] = sqrt(pow(a.x - b.x,2)+pow(a.y - b.y,2) + pow(a.z - b.z,2));
22     side[1] = sqrt(pow(a.x - c.x,2)+pow(a.y - c.y,2) + pow(a.z - c.z,2));
23     side[2] = sqrt(pow(c.x - b.x,2)+pow(c.y - b.y,2) + pow(c.z - b.z,2));
24  
25     //不能構成三角形;
26     if
 
(side[0]+side[1]<=side[2] || side[0]+side[2]<=side[1] || side[1]+side[2]<=side[0]) return area;
27  
28     //利用海倫公式。s=sqr(p*(p-a)(p-b)(p-c));
29     double p = (side[0]+side[1]+side[2])/2; //半周長;
30     area = sqrt(p*(p-side[0])*(p-side[1])*(p-side[2]));
31  
32     return area;
33 }
34 int main()
35
 
 {
36     int n;
37     while(cin>>n)
38     {
39         double area = 0.0;
40         double max_area = 0.0;
41         Point p[n];
42         for(int i=0;i<n;i++)
43         {
44             cin>>p[i].color>>p[i].x>>p[i].y>>p[i].z;
45         }
46         for(int i=0;i<n;i++)
47         {
48             for(int j=i+1;j<n;j++)
49             {
50                 for(int k=j+1;k<n;k++)
51                 {
52                     area = count_triangle_area(p[i],p[j],p[k]);
53                     if(((p[i].color == p[j].color) && (p[i].color == p[k].color))
54                         ||((p[i].color != p[j].color)&&(p[i].color != p[k].color)&&(p[j].color != p[k].color)))
55                     {
56                         max_area = max(max_area,area);
57                     }
58                 }
59             }
60         }
61         cout.setf(ios::fixed);//位數不夠自動補0（若需要自動補0，在cout之前進行補0的定義，cout中加入“<<fixed”）
62         cout << fixed <<setprecision(5)<<max_area<<endl;
63     }
64     return 0;
65 }