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

int main(){
int a[6];
for (int i = 0; i < 6; ++i) {
	cin>>a[i];
}
sort(a,a+6);
double sum=0;
for (int i = 1; i <= 4; ++i) {
	sum+=a[i];
}
printf("%.2f",sum/4.0);

}