#include <bits/stdc++.h>
#define rep(a,n) for (ll a = 0; a < (n); ++a)
using namespace std;
//using namespace atcoder;
using ll = long long;
typedef pair<ll,ll> P;
typedef pair<ll,P> PP;
typedef vector<vector<int> > Graph;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
const ll INF = 1e18;

int main(){
    double p,q,r;
    cin >> p >> q >> r;
    double ans = 0;
    double s = p+q+r;
    chmax(ans,(p+q)/s);
    chmax(ans,(q+r)/s);
    chmax(ans,(r+p)/s);
    printf("%.16lf\n",ans);
    return 0;
}