#include<iostream>#include<cmath>using namespace std;bool TriangleArea(double a, double b, double c, double &area){     if(a + b <= c || fabs(a - b) >= c || a <= 0 || b <= 0 || c <= 0)     {         return false;     }     double s;     s = (a + b + c) / 2.0;     area = sqrt(s * (s - a) * (s - b) * (s - c));     return true;}void main(){     double area, a, b, c;     while(cin >> a >> b >> c)     {          area = 0;          if(a == 0 && b == 0 && c == 0)          {              break;          }          if(TriangleArea(a, b, c, area))          {              cout << "面积为: " << area << endl;          }          else          {              cout << "不能够成三角形. " << endl;          }     }}