```

```
#include<bits/stdc++.h>
using namespace std;
double a,b,c,p,ans;
int main()
{
	cin>>a>>b>>c;
	p=(a+b+c)/2;
	ans=sqrt(p*(p-a)*(p-b)*(p-c));
	printf("%.2lf",ans);
	return 0;
}
```