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

signed main(){
  cout << fixed << setprecision(2);
  vector<int> A(6);
  for( int i = 0; i < 6; i++ ) cin >> A.at(i);
  sort(A.begin(), A.end());
  int T = 0;
  for( int i = 1; i < 5; i++ ) T += A.at(i);
  double ans = (double)T/4.0;
  cout << ans << endl;
}