#include <bits/stdc++.h>
using namespace std;

int main() {
	int a[6];cin>>a[0]>>a[1]>>a[2]>>a[3]>>a[4]>>a[5];sort(a,a+6);
	printf("%.2f\n",(double)(a[1]+a[2]+a[3]+a[4])/4);
	return 0;
}