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

int main (void) {
	int a[6];
	double ans;

	scanf("%d %d %d %d %d %d", &a[0], &a[1], &a[2], &a[3], &a[4], &a[5]);
	sort(a, a + 6);
	ans = (a[1] + a[2] + a[3] + a[4]) / 4.0;

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

	return 0;
}