#include <bits/stdc++.h>
using namespace std;
int main(){
  cout << fixed << setprecision(2);
  vector<int> S(6);
  for (int i = 0; i < 6; i++){
    cin >> S[i];
  }
  sort(S.begin(), S.end());
  cout << (double) (S[1] + S[2] + S[3] + S[4]) / 4 << endl;
}