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

#define ll long long
#define rep(i, n) for (int i = 0; i < (n); i++)
#define P pair<int, int>

int main() {
  int p, q, r;
  cin >> p >> q >> r;


  cout << fixed << setprecision(15) << (double)max({p+q, q+r, r+p}) / (double)(p+q+r) << endl;



}