#include <bits/stdc++.h>
#define rep(i, ss, ee) for (int i = ss; i < ee; ++i)
using namespace std;

double solve() {
  double ans = 0;
  vector<int> v(6);
  rep(i, 0, 6) { cin >> v[i]; }
  sort(v.begin(), v.end());
  rep(i, 1, 5) { ans += v[i]; }
  ans /= 4;
  return ans;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  printf("%.2f",solve());
  getchar();
}