#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
  #define _GLIBCXX_DEBUG
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  vector<int> a(6);
  rep(i, 6) cin >> a[i];
  sort(a.begin(), a.end());
  cout << double(accumulate(a.begin() + 1, a.end() - 1, 0.0)) / 4 << endl;
  return 0;
}