#include <iostream>
#include <algorithm>
#include <iomanip>
using namespace std;

int main() {
  int a[6];
  for (auto& e : a) cin >> e;
  sort(a, a + 6);
  int sum = 0;
  for (int i = 1; i <= 4; i++) {
    sum += a[i];
  }
  cout << fixed << setprecision(2) << sum / 4.0 << endl;
  return 0;
}