#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)(n);i++)
using namespace std;
using ll = long long ;
using P = pair<int,int> ;
using pll = pair<long long,long long>;
constexpr int INF = 1e9;
constexpr long long LINF = 1e17;
constexpr int MOD = 1000000007;
constexpr double PI = 3.14159265358979323846;

int main(){
    vector<int> pp(6);
    rep(i,6) cin >> pp[i];
    sort(pp.begin(),pp.end());
    int ans = 0;
    for(int i=1;i<=4;i++){
        ans += pp[i];
    }
    double k = ans / 4.0;
    printf("%.2f\n",k);
    return 0;
}