#include <bits/stdc++.h>
using namespace std;

signed main(){
  long double a,b,c;cin>>a>>b>>c;
  //d=cos(a)
  long double d=((b*b+c*c-a*a)/(2*b*c));
  //e=sin(a)
  long double e=sqrt(1-d*d);
  //s=abc
  long double s=b*c*e/2;
  cout<<fixed<<setprecision(15);
  cout<<s*2/(a+b+c)<<endl;
}