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

template<typename T, typename U> void cmax(T &a, U b) { if (a < b) a = b; }
template<typename T, typename U> void cmin(T &a, U b) { if (a > b) a = b; }

signed main() {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);

  int N = 3;
  vector<int> A(N);
  for (int i = 0; i < N; i++) cin >> A.at(i);

  sort(A.begin(), A.end());
  int acc = accumulate(A.begin(), A.end(), 0);
  
  cout << fixed << setprecision(10) << (double) A.at(1) / acc + (double) A.at(2) / acc << "\n";
}