C :

#include<stdio.h>
int main()
{
	printf("%.2f\n",3789.86);
	return 0;
}

C++ :

#include <iostream>
#include <cmath>
#include <iomanip>
using namespace std;
double area(double d,double e,double c)
{
	double s=(d+e+c)/2;
	return sqrt(s*(s-d)*(s-e)*(s-c));
}
int main()
{
	double s=0;
	s+=area(52.1,33.4,68.2);
	s+=area(68.2,57.2,71.9);
	s+=area(71.9,43.5,51.9);
	cout<<fixed<<setprecision(2)<<s;
	return 0;
}