#include<iostream>
using namespace std;
int main()
{
	int a,b,c;
	float p,A;
	cout<<"a="; cin>>a;
	cout<<"b="; cin>>b;
	cout<<"c="; cin>>c;
	p=(float)(a+b+c)/2;
	A=sqrt(p*(p-a)*(p-b)*(p-c));
	cout<<"aria este "<<A;
	return 0;
}