#include <iostream>
#include <vector>
#include <algorithm>
#include <iomanip>
using namespace std;
int main()
{
	vector<int> S;
	int a = 0;
	S.resize(6);
	cin >> S[0] >> S[1] >> S[2] >> S[3] >> S[4] >> S[5];
	sort(S.begin(), S.end());
	for (int i = 1; i < 5; i++) a += S[i];
	cout << fixed;
	cout << setprecision(2) << (double)(a / 4) << endl;
	return 0;
}