#include<iostream>
#include<stdio.h>
#include<string>
#include<vector>
#include<map>
#include<math.h>
#include<algorithm>
#include<iomanip>

using namespace std;

vector <double > s;

int main() {
	s.resize(6);
	for (int i = 0; i < 6; i++)cin >> s[i];
	sort(s.begin(), s.end());
	double ans = 1.0 / 4 * (s[1] + s[2] + s[3] + s[4]);
	cout << setprecision(5) << ans << endl;
	return 0;
}