#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>

using namespace std;

int main() {
  vector<int> v(6);
  for (int i=0; i<6; i++) {
    cin >> v[i];
  }

  sort(v.begin(), v.end());

  printf("%0.2lf\n", accumulate(v.begin()+1, v.end()-1, 0)/4.0);
  return 0;
}