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

int main() {
    vector<int> a(6);
    for (int &e : a) cin >> e;
    sort(a.begin(), a.end());
    
    int sum = accumulate(a.begin() + 1, a.begin() + 5, 0);
    
    double ans = (double)sum / 4.0;
    
    cout << fixed << setprecision(2) << ans << '\n';
    return 0;
}