C :

#include <stdio.h>
#include <math.h>
int main()
{
	double a,b,c,d;
    scanf("%lf%lf%lf",&a,&b,&c);
    d=(a+b+c)/2;
    if(a+b>c && a+c>b && b+c>a) 
        printf("%.1f",sqrt(d*(d-a)*(d-b)*(d-c)));
    else printf("false");
	return 0;
}

C++ :

#include<stdio.h>
#include<math.h>
#include<stdlib.h>
int main(){
	int a,b,c;
	double d,s;
	scanf("%d%d%d",&a,&b,&c);
	if((a+b>c)&&(a+c>b)&&(b+c>a)&&
	(abs(a-b)<c)&&(abs(b-c)<a)&&(abs(a-c)<b)){
		d=(a+b+c)/2;
		s=sqrt(d*(d-a)*(d-b)*(d-c));
		printf("%.1lf\n",s);
	}
	else printf("false\n");
	return 0;
}

Pascal :

program xx;
var a,b,c:integer;
    d,s:real;
begin
    readln(a,b,c);
    if ((a+b)>c) and((a+c)>b) and((b+c)>a)
      then begin
           d:=(a+b+c)/2;
           s:=sqrt(d*(d-a)*(d-b)*(d-c));
           writeln(s:3:1);
           end
      else writeln('false');

end.

Python :

# coding=utf-8
a,b,c=input().split()
a=float(a)
b=float(b)
c=float(c)
if a+b>c and a+c>b and b+c>a:
    d=(a+b+c)/2
    s=round((d*(d-a)*(d-b)*(d-c))**0.5,1)
    print(s)
else:
    print("false")