C :

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

C++ :

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