#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
int main(){
    vector<int> s(6);
    cin>>s[0]>>s[1]>>s[2]>>s[3]>>s[4]>>s[5];
    sort(s.begin(),s.end());
    s[0]=s[1]+s[2]+s[3]+s[4];
    if(s[0]%4==0){
        cout<<s[0]/4<<".00"<<endl;
    }else if(s[0]%4==2){
        cout<<s[0]/4<<".50"<<endl;
    }else if(s[0]%4==1){
        cout<<s[0]/4<<".25"<<endl;
    }else{
        cout<<s[0]/4<<".75"<<endl;
    }
}