#include <iostream>
#include <iomanip>
#include <algorithm>
typedef unsigned long long ul;
typedef signed long long ll;

int main(void)
{
  std::cin.tie(0);
  std::ios::sync_with_stdio(false);
  std::cout << std::fixed << std::setprecision(2);
  int s[6];
  for (int i = 0; i < 6; ++i) std::cin >> s[i];
  std::sort(s, s+6);
  std::cout << (s[1] + s[2] + s[3] + s[4]) / 4.0 << std::endl;
  return 0;
}