C++ :

#include<iostream>
#include<math.h>
#include<stdio.h>
using namespace std;
  
int main(){
    double a,b,c,p,s;
    cin>>a>>b>>c;
    if(a*a+b*b==c*c||a*a+c*c==b*b||c*c+b*b==a*a)
	{
		p=(a+b+c)/2;
		s=sqrt(p*(p-a)*(p-b)*(p-c));
		cout<<"s=";printf("%.2f\n",s);
	}
    else cout<<"No!";
    return 0;
}

Pascal :

var
a,b,c,p,s:real;
 begin
   readln(a,b,c);
   if (a*a+b*b=c*c) or(a*a+c*c=b*b) or(b*b+c*c=a*a)  then
   begin p:=(a+b+c)/2; s:=sqrt(p*(p-a)*(p-b)*(p-c)); writeln('s=',s:0:2) ;end
   else writeln('No!');

 end.