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;
}