#include<bits/stdc++.h>

using namespace std;
string ans[]={"00","25","50","75"};
int main(){
    vector<int> num(6);
    for(int i=0;i<6;i++)cin>>num[i];
    sort(num.begin(),num.end());
    int sum=0;
    for(int i=1;i<5;i++)sum+=num[i];
    cout<<sum/4<<"."<<ans[sum%4]<<endl;
    
    return 0;
}