#include <bits/stdc++.h>
using namespace std;
int main() {
       	vector<int> s(6);
       	for(int i = 0; i < 6; i++) cin >> s[i];
       	sort(s.begin(), s.end());
       	double ans;
       	ans = (s[1] * 1.0 + s[2] * 1.0 + s[3] * 1.0 + s[4] * 1.0) / 4;

       	printf("%.2f\n", ans);

       	return 0;
}