C :

#include<stdio.h>
#include<math.h>
int main(){
double a,b,c,s,L;
scanf("%lf %lf %lf",&a,&b,&c);
s=(a+b+c)/2;
L=sqrt(s*(s-a)*(s-b)*(s-c));
printf("%.2lf",L);
return 0;
}

C++ :

#include <stdio.h>
#include <math.h>
int main() {
	float a, b, c, s, area;
	scanf("%f %f %f", &a, &b, &c);
	s = (a + b + c) * 0.5;
	area = sqrt(s * (s - a) * (s - b) * (s - c));
	printf("%.2f\n", area);
	return 0;
}

Pascal :

var
  a,b,c,d,s:double;
begin
  readln(a,b,c);
  d:=(a+b+c)/2;
  s:=sqrt(d*(d-a)*(d-b)*(d-c));
  writeln(s:0:2);
end.

Java :

import java.util.*;
public class Main {
	public static void main(String args[]) {
		Scanner cin=new Scanner(System.in);
		double a,b,c;
		double p;
		double hl;
		a=cin.nextDouble();
		b=cin.nextDouble();
		c=cin.nextDouble();
		p=(a+b+c)/2;
		hl=Math.sqrt(p*(p-a)*(p-b)*(p-c));
		System.out.printf("%.2f",hl);
	}
}

Python :

from math import sqrt
a,b,c = [float(x) for x in raw_input().split()]
p = (a+b+c)/2
print "%.2f" %sqrt(p*(p-a)*(p-b)*(p-c))