#include <iostream>
#include <algorithm>
#include <cstdio>
#include <vector>
#include <numeric>
using namespace std;

int main()
{
    vector<int> s(6);
    for(auto& e: s) cin>>e;
    sort(begin(s), end(s));
    printf("%.2f\n", accumulate(begin(s)+1, end(s)-1, 0)*0.25);
}