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

int main(){
    vector<double>vec;
    double S[6] = {};
    double sum = 0;
    for(int i = 0; i < 6; ++i){ cin >> S[i]; vec.push_back(S[i]); }
    sort(begin(vec),end(vec));
    cout << fixed << setprecision(2) << accumulate(vec.begin()+1,vec.end()-1,0.0) / 4.0 << endl;
    return 0;
}