#ifndef INCLUDED_MAIN
#define INCLUDED_MAIN

#include __FILE__

int main(){
    ld a,b,c; cin>>a>>b>>c;
    ld S=heron(a,b,c);
    ld ans=2*S/(a+b+c);
    cout<<fixed<<setprecision(10)<<ans<<nl;
}

/////// library zone ///////
#else
#include <bits/stdc++.h>
#include <atcoder/segtree>
using namespace std;
#define rep(i,n) for(ll i=0;i<n;i++)
#define srep(i,l,r) for(ll i=l;i<=r;i++)
using ll = long long;
using ld = long double;
const ll mod=998244353;
#define vout(v) for(auto i :v) cout<<i<<" ";
#define INF 9223300000000000000ll
#define Winf 5e12
#define nl "\n"
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define vl vector<ll>
#define vc vector<char>

ld heron(ld a,ld b,ld c) {
    ld t=(a+b+c)/2.0;
    ld tt=t*(t-a)*(t-b)*(t-c);
    return sqrtl(tt);
}


ll op(ll a,ll b) {return a+b;}
ll e() {return 0ll;}



template<typename T> bool chmin(T& a, T b){if(a > b){a = b; return true;} return false;}
template<typename T> bool chmax(T& a, T b){if(a < b){a = b; return true;} return false;}

void no() { cout<<"No"<<nl;}
void yes() { cout<<"Yes"<<nl;}
void yn(bool a) {
    cout<<(a ? "Yes":"No")<<nl;
}

ll sum(vector<ll>& a) {
    ll ans=0;
    for(auto i:a) ans+=i;
    return ans;
}



ll modpow(ll fl, ll po, ll mode) {  // mode: 0=modなし, 1=modあり
    ll ret=1;
    if (mode) {
        while (po>0) {
            if (po&1) ret=(ret*fl)%mod;
            fl=(fl*fl)%mod;
            po>>=1;
        }
    } else {
        while (po>0) {
            if(po&1) ret*=fl;
            fl*=fl;
            po>>=1;
        }
    }
    return ret;
}

#endif