import java.io.*;
public class sanjiaoxing{
public static void main(String arg[]){
int a=0,b=0,c=0;
   String s;
   try{//輸入三個數(將輸入的三個字符化為整數)
      System.out.print("請輸入三角形三邊  ");
      System.out.print("Enter a:");
      BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
      s=br.readLine();
      a=Integer.parseInt(s);
      System.out.print("Enter b:");
      s=br.readLine();
      b=Integer.parseInt(s);
      System.out.print("Enter c:");
      s=br.readLine();
      c=Integer.parseInt(s);
     System.out.println(a+" "+b+" "+c+" ");
    }catch(IOException e){}
    double S,p;
  if((a+b)<=c&&(a+c)<=b&&(b+c)<=a&&(a-b)<=c&&(a-c)<=b&&
  (b-c)<=a&&(b-a)<=c&&(c-a)<=b&&(c-b)<=a){//三邊不符合條件
      int min;
      if(a>b) min=b;//求最小邊
       else min=a;
      if(c>min) min=min;
       else min=c;     //求最小邊
       p = (3*min)/ 2;  
     S=Math.sqrt(p * (p - min) *(p - min)*(p - min));
     System.out.println("三角形的面積為 S="+S);
           
    }
  else{   p = (a + b +c) / 2;//三邊符合條件
          S=Math.sqrt(p * (p - a) * (p- b) * (p- c));
     System.out.println("三角形的面積為 S="+S);
    }
}
}