#include<bits/stdc++.h>
#define int long long
#define double long double
using namespace std;
signed main(){
    double a,b,c;cin>>a>>b>>c;
    double s=(a+b+c)/2;
    cout<<fixed<<setprecision(18)<<sqrt(s*(s-a)*(s-b)*(s-c))/s<<endl;
}