#include <bits/stdc++.h>
using namespace std;

int main() {
    vector<int> v(6);
    for (auto& i : v) cin >> i;
    sort(v.begin(), v.end());
    double sum = 0.;
    for (int i = 1; i < 5; i++) sum += v[i];
    cout << sum / 4. << endl;

    return 0;
}