#include <iostream>
#include <algorithm>
using namespace std;

int main() {
	int s[6];
	for (int i = 0; i <= 5; i++) cin >> s[i];
	sort(s, s+6);

	int sum = 0;
	for (int j = 1; j <= 4; j++) sum += s[j];

	printf("%.2f\n%", double(sum) / 4);
	return 0;
}