tj

#include<cstdio>
#include<iostream>
#include<cmath>
using namespace std;
int main(){
double a,b,c;
double d;
cin >>a>>b>>c;
double s=(a+b+c)/2;
double r=s*(s-a)(s-b)(s-c);
d=sqrt(r);
printf("%.2f",d);

return 0;

}