#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main(){
  vector<int> S(6);
  cin>>S[0]>>S[1]>>S[2]>>S[3]>>S[4]>>S[5];
  sort(S.begin(),S.end());
  cout<<fixed<<setprecision(2);
  cout<<(S[1]+S[2]+S[3]+S[4])/4.0<<endl;
}